Re: [ai-geostats] Re: Geostats Scam?
Isobel, I keep in mind at all times that wonderful sentence in Clark (1979), "Systematic errors, be they sampling , analytical, or whatever, will not be picked up by geostatistics and will be transferred to any estimates produced." (p. 119) Isobel,this wisdomshould be included in the disclaimer of any geostatistical report. If one looks at the lead paper of the Australian Best Practices Volume (proper citation not available because I have misplaced thebook). More than 50% of gold deposits fail to achieve nameplate output in the first year of production due to grade shortfall (David Harquail, Graham Clow and and Australian masters thesis). Then things improve, not from statistics, but using fudge factors(mine call factor, cutting, whatever). Mike Armitage, Managing Director of SRK, is on record in the SRK newsletter stating that the predictability of geostatistics is no better today than at any time in the past. I took issue with Danie Krige in the SAJG for saying, in 2001, the framework of geostatistics included all the necessary elements and no further discoveries need be made. In my experience, the issue is sampling, splitting, analysis, and execution. By the time a geological sample gets to a 30 gram aliquot, the likelihood of that 30 grams representing 1,000,000 grams of rock is probably compromised about 50% of the time. So we respond, in ignorance,by taking thousands of samples. In my opinion, 33 samples will suffice in am stope, giving two extra sample for more confidence Need to take large enough samples to be representative though. Got to avoid the systematic error of not having a representative sample for the region, deposit, stope, etc. I cringe when I see geostatistics applied to ground water projects or remediation projects, or astrophysics. Ask yourself whether asteroid size distribution as sampled mightsuffer a 'nugget effect'. Francis T. Manns, Ph.D., P.Geo. (Ont) Artesian Geological Research Toronto, Ontario And the following sense from Jim Tilsley also need to be integrated Fran, Questioning geo-stats is an advancement in understanding. This is good for everyone and everything involved. The point most overlooked in the 'equation' is the first half of the term. GEO! I, as you know, have always objected to statistics being the main focus. FIRST do the geology. Then we may find that some sort of statistical treatment can be applied rationally. As we have discussed before on many occasions, Kreiging works wonderfully on mature gold placers of the Wits. The trouble comes in when attempts are made to apply it to another type of mineralized zone, one that has not been deposited under the same energy regime as the Wits. There can be a relationship between grade - a parameter fraught with difficulties in the details - and relative position in respect to another grade, only when there is some sort of energy gradient that ties the two together - as in the paleo-placers for which the approach was developed. Since the energy budget correlates with the distance from the centre of the channel, decreasing toward the limits of flow - (Hydraulics 101) detrital heavy mineral concentration can be expected to reflect the mechanical energy applied, and some sort of distance/grade relationship is plausible. (The Carbon Leader gold mineralization is another matter, but if the algae mats acted as chemical traps and there was some difference in total flow (volume) from a 'channel' axis across the mats, one could expect to see a similar distribution of values, but the geological controls and the difference in depositional environment must be considered.) Statistics, in my experience, may be applicable in ore reserve estimation, (and will solve many problems if properly applied) providing they are used with due reference to the geological controls on deposition. And this applies to mechanical and chemical mineralization systems equally. The chemical systems are usually the more difficult to deal with. Jim - Original Message - From: Isobel Clark To: Stephen Henley Cc: AI Geostats mailing list Sent: Wednesday, February 08, 2006 10:07 AM Subject: [ai-geostats] Re: Geostats Scam? And don't forget the 27 page article by Philip Watson "Matheronian geostatistics - Quo Vadis?" in Mathematical Geology, vol 18, pp 93-117. 24 pages on what a confidence trick geostatistics is. There are response letters in that volume and later volumes from members of the geostatistical community. A wonderful example of neither side listening. Bear in mind when you read this article that it was not refereed before publication. In fact, this is a very good paper to illustrate the enormous difference which can occur when you approach a problem from a completely different direction. What baffled me for a long time is that their argument is that where you have more data, you have
Re: [ai-geostats] Re: Geostats Scam?
Isobel, I keep in mind at all times that wonderful sentence in Clark (1979), "Systematic errors, be they sampling , analytical, or whatever, will not be picked up by geostatistics and will be transferred to any estimates produced." (p. 119) Isobel,this wisdomshould be included in the disclaimer of any geostatistical report. If one looks at the lead paper of the Australian Best Practices Volume (proper citation not available because I have misplaced thebook). More than 50% of gold deposits fail to achieve nameplate output in the first year of production due to grade shortfall (David Harquail, Graham Clow and and Australian masters thesis). Then things improve, not from statistics, but using fudge factors(mine call factor, cutting, whatever). Mike Armitage, Managing Director of SRK, is on record in the SRK newsletter stating that the predictability of geostatistics is no better today than at any time in the past. I took issue with Danie Krige in the SAJG for saying, in 2001, the framework of geostatistics included all the necessary elements and no further discoveries need be made. In my experience, the issue is sampling, splitting, analysis, and execution. By the time a geological sample gets to a 30 gram aliquot, the likelihood of that 30 grams representing 1,000,000 grams of rock is probably compromised about 50% of the time. So we respond, in ignorance,by taking thousands of samples. In my opinion, 33 samples will suffice in am stope, giving two extra sample for more confidence Need to take large enough samples to be representative though. Got to avoid the systematic error of not having a representative sample for the region, deposit, stope, etc. I cringe when I see geostatistics applied to ground water projects or remediation projects, or astrophysics. Ask yourself whether asteroid size distribution as sampled mightsuffer a 'nugget effect'. Francis T. Manns, Ph.D., P.Geo. (Ont) Artesian Geological Research Toronto, Ontario And the following sense from Jim Tilsley also need to be integrated Fran, Questioning geo-stats is an advancement in understanding. This is good for everyone and everything involved. The point most overlooked in the 'equation' is the first half of the term. GEO! I, as you know, have always objected to statistics being the main focus. FIRST do the geology. Then we may find that some sort of statistical treatment can be applied rationally. As we have discussed before on many occasions, Kreiging works wonderfully on mature gold placers of the Wits. The trouble comes in when attempts are made to apply it to another type of mineralized zone, one that has not been deposited under the same energy regime as the Wits. There can be a relationship between grade - a parameter fraught with difficulties in the details - and relative position in respect to another grade, only when there is some sort of energy gradient that ties the two together - as in the paleo-placers for which the approach was developed. Since the energy budget correlates with the distance from the centre of the channel, decreasing toward the limits of flow - (Hydraulics 101) detrital heavy mineral concentration can be expected to reflect the mechanical energy applied, and some sort of distance/grade relationship is plausible. (The Carbon Leader gold mineralization is another matter, but if the algae mats acted as chemical traps and there was some difference in total flow (volume) from a 'channel' axis across the mats, one could expect to see a similar distribution of values, but the geological controls and the difference in depositional environment must be considered.) Statistics, in my experience, may be applicable in ore reserve estimation, (and will solve many problems if properly applied) providing they are used with due reference to the geological controls on deposition. And this applies to mechanical and chemical mineralization systems equally. The chemical systems are usually the more difficult to deal with. Jim - Original Message - From: Isobel Clark To: Stephen Henley Cc: AI Geostats mailing list Sent: Wednesday, February 08, 2006 10:07 AM Subject: [ai-geostats] Re: Geostats Scam? And don't forget the 27 page article by Philip Watson "Matheronian geostatistics - Quo Vadis?" in Mathematical Geology, vol 18, pp 93-117. 24 pages on what a confidence trick geostatistics is. There are response letters in that volume and later volumes from members of the geostatistical community. A wonderful example of neither side listening. Bear in mind when you read this article that it was not refereed before publication. In fact, this is a very good paper to illustrate the enormous difference which can occur when you approach a problem from a completely different direction. What baffled me for a long time is that their argument is that where you have more data, you have
Re: [ai-geostats] Re: Geostats Scam?
Isobel, I keep in mind at all times that wonderful sentence in Clark (1979), "Systematic errors, be they sampling , analytical, or whatever, will not be picked up by geostatistics and will be transferred to any estimates produced." (p. 119) Isobel,this wisdomshould be included in the disclaimer of any geostatistical report. If one looks at the lead paper of the Australian Best Practices Volume (proper citation not available because I have misplaced thebook). More than 50% of gold deposits fail to achieve nameplate output in the first year of production due to grade shortfall (David Harquail, Graham Clow and and Australian masters thesis). Then things improve, not from statistics, but using fudge factors(mine call factor, cutting, whatever). Mike Armitage, Managing Director of SRK, is on record in the SRK newsletter stating that the predictability of geostatistics is no better today than at any time in the past. I took issue with Danie Krige in the SAJG for saying, in 2001, the framework of geostatistics included all the necessary elements and no further discoveries need be made. In my experience, the issue is sampling, splitting, analysis, and execution. By the time a geological sample gets to a 30 gram aliquot, the likelihood of that 30 grams representing 1,000,000 grams of rock is probably compromised about 50% of the time. So we respond, in ignorance,by taking thousands of samples. In my opinion, 33 samples will suffice in am stope, giving two extra sample for more confidence Need to take large enough samples to be representative though. Got to avoid the systematic error of not having a representative sample for the region, deposit, stope, etc. I cringe when I see geostatistics applied to ground water projects or remediation projects, or astrophysics. Ask yourself whether asteroid size distribution as sampled mightsuffer a 'nugget effect'. Francis T. Manns, Ph.D., P.Geo. (Ont) Artesian Geological Research Toronto, Ontario And the following sense from Jim Tilsley also need to be integrated Fran, Questioning geo-stats is an advancement in understanding. This is good for everyone and everything involved. The point most overlooked in the 'equation' is the first half of the term. GEO! I, as you know, have always objected to statistics being the main focus. FIRST do the geology. Then we may find that some sort of statistical treatment can be applied rationally. As we have discussed before on many occasions, Kreiging works wonderfully on mature gold placers of the Wits. The trouble comes in when attempts are made to apply it to another type of mineralized zone, one that has not been deposited under the same energy regime as the Wits. There can be a relationship between grade - a parameter fraught with difficulties in the details - and relative position in respect to another grade, only when there is some sort of energy gradient that ties the two together - as in the paleo-placers for which the approach was developed. Since the energy budget correlates with the distance from the centre of the channel, decreasing toward the limits of flow - (Hydraulics 101) detrital heavy mineral concentration can be expected to reflect the mechanical energy applied, and some sort of distance/grade relationship is plausible. (The Carbon Leader gold mineralization is another matter, but if the algae mats acted as chemical traps and there was some difference in total flow (volume) from a 'channel' axis across the mats, one could expect to see a similar distribution of values, but the geological controls and the difference in depositional environment must be considered.) Statistics, in my experience, may be applicable in ore reserve estimation, (and will solve many problems if properly applied) providing they are used with due reference to the geological controls on deposition. And this applies to mechanical and chemical mineralization systems equally. The chemical systems are usually the more difficult to deal with. Jim - Original Message - From: Isobel Clark To: Stephen Henley Cc: AI Geostats mailing list Sent: Wednesday, February 08, 2006 10:07 AM Subject: [ai-geostats] Re: Geostats Scam? And don't forget the 27 page article by Philip Watson "Matheronian geostatistics - Quo Vadis?" in Mathematical Geology, vol 18, pp 93-117. 24 pages on what a confidence trick geostatistics is. There are response letters in that volume and later volumes from members of the geostatistical community. A wonderful example of neither side listening. Bear in mind when you read this article that it was not refereed before publication. In fact, this is a very good paper to illustrate the enormous difference which can occur when you approach a problem from a completely different direction. What baffled me for a long time is that their argument is that where you have more data, you have
Re: [ai-geostats] Re: Geostats Scam?
Isobel, I keep in mind at all times that wonderful sentence in Clark (1979), "Systematic errors, be they sampling , analytical, or whatever, will not be picked up by geostatistics and will be transferred to any estimates produced." (p. 119) Isobel,this wisdomshould be included in the disclaimer of any geostatistical report. If one looks at the lead paper of the Australian Best Practices Volume (proper citation not available because I have misplaced thebook). More than 50% of gold deposits fail to achieve nameplate output in the first year of production due to grade shortfall (David Harquail, Graham Clow and and Australian masters thesis). Then things improve, not from statistics, but using fudge factors(mine call factor, cutting, whatever). Mike Armitage, Managing Director of SRK, is on record in the SRK newsletter stating that the predictability of geostatistics is no better today than at any time in the past. I took issue with Danie Krige in the SAJG for saying, in 2001, the framework of geostatistics included all the necessary elements and no further discoveries need be made. In my experience, the issue is sampling, splitting, analysis, and execution. By the time a geological sample gets to a 30 gram aliquot, the likelihood of that 30 grams representing 1,000,000 grams of rock is probably compromised about 50% of the time. So we respond, in ignorance,by taking thousands of samples. In my opinion, 33 samples will suffice in am stope, giving two extra sample for more confidence Need to take large enough samples to be representative though. Got to avoid the systematic error of not having a representative sample for the region, deposit, stope, etc. I cringe when I see geostatistics applied to ground water projects or remediation projects, or astrophysics. Ask yourself whether asteroid size distribution as sampled mightsuffer a 'nugget effect'. Francis T. Manns, Ph.D., P.Geo. (Ont) Artesian Geological Research Toronto, Ontario And the following sense from Jim Tilsley also need to be integrated Fran, Questioning geo-stats is an advancement in understanding. This is good for everyone and everything involved. The point most overlooked in the 'equation' is the first half of the term. GEO! I, as you know, have always objected to statistics being the main focus. FIRST do the geology. Then we may find that some sort of statistical treatment can be applied rationally. As we have discussed before on many occasions, Kreiging works wonderfully on mature gold placers of the Wits. The trouble comes in when attempts are made to apply it to another type of mineralized zone, one that has not been deposited under the same energy regime as the Wits. There can be a relationship between grade - a parameter fraught with difficulties in the details - and relative position in respect to another grade, only when there is some sort of energy gradient that ties the two together - as in the paleo-placers for which the approach was developed. Since the energy budget correlates with the distance from the centre of the channel, decreasing toward the limits of flow - (Hydraulics 101) detrital heavy mineral concentration can be expected to reflect the mechanical energy applied, and some sort of distance/grade relationship is plausible. (The Carbon Leader gold mineralization is another matter, but if the algae mats acted as chemical traps and there was some difference in total flow (volume) from a 'channel' axis across the mats, one could expect to see a similar distribution of values, but the geological controls and the difference in depositional environment must be considered.) Statistics, in my experience, may be applicable in ore reserve estimation, (and will solve many problems if properly applied) providing they are used with due reference to the geological controls on deposition. And this applies to mechanical and chemical mineralization systems equally. The chemical systems are usually the more difficult to deal with. Jim - Original Message - From: Isobel Clark To: Stephen Henley Cc: AI Geostats mailing list Sent: Wednesday, February 08, 2006 10:07 AM Subject: [ai-geostats] Re: Geostats Scam? And don't forget the 27 page article by Philip Watson "Matheronian geostatistics - Quo Vadis?" in Mathematical Geology, vol 18, pp 93-117. 24 pages on what a confidence trick geostatistics is. There are response letters in that volume and later volumes from members of the geostatistical community. A wonderful example of neither side listening. Bear in mind when you read this article that it was not refereed before publication. In fact, this is a very good paper to illustrate the enormous difference which can occur when you approach a problem from a completely different direction. What baffled me for a long time is that their argument is that where you have more data, you have
Re: [ai-geostats] Re: Geostats Scam?
Isobel, I keep in mind at all times that wonderful sentence in Clark (1979), "Systematic errors, be they sampling , analytical, or whatever, will not be picked up by geostatistics and will be transferred to any estimates produced." (p. 119) Isobel,this wisdomshould be included in the disclaimer of any geostatistical report. If one looks at the lead paper of the Australian Best Practices Volume (proper citation not available because I have misplaced thebook). More than 50% of gold deposits fail to achieve nameplate output in the first year of production due to grade shortfall (David Harquail, Graham Clow and and Australian masters thesis). Then things improve, not from statistics, but using fudge factors(mine call factor, cutting, whatever). Mike Armitage, Managing Director of SRK, is on record in the SRK newsletter stating that the predictability of geostatistics is no better today than at any time in the past. I took issue with Danie Krige in the SAJG for saying, in 2001, the framework of geostatistics included all the necessary elements and no further discoveries need be made. In my experience, the issue is sampling, splitting, analysis, and execution. By the time a geological sample gets to a 30 gram aliquot, the likelihood of that 30 grams representing 1,000,000 grams of rock is probably compromised about 50% of the time. So we respond, in ignorance,by taking thousands of samples. In my opinion, 33 samples will suffice in am stope, giving two extra sample for more confidence Need to take large enough samples to be representative though. Got to avoid the systematic error of not having a representative sample for the region, deposit, stope, etc. I cringe when I see geostatistics applied to ground water projects or remediation projects, or astrophysics. Ask yourself whether asteroid size distribution as sampled mightsuffer a 'nugget effect'. Francis T. Manns, Ph.D., P.Geo. (Ont) Artesian Geological Research Toronto, Ontario And the following sense from Jim Tilsley also need to be integrated Fran, Questioning geo-stats is an advancement in understanding. This is good for everyone and everything involved. The point most overlooked in the 'equation' is the first half of the term. GEO! I, as you know, have always objected to statistics being the main focus. FIRST do the geology. Then we may find that some sort of statistical treatment can be applied rationally. As we have discussed before on many occasions, Kreiging works wonderfully on mature gold placers of the Wits. The trouble comes in when attempts are made to apply it to another type of mineralized zone, one that has not been deposited under the same energy regime as the Wits. There can be a relationship between grade - a parameter fraught with difficulties in the details - and relative position in respect to another grade, only when there is some sort of energy gradient that ties the two together - as in the paleo-placers for which the approach was developed. Since the energy budget correlates with the distance from the centre of the channel, decreasing toward the limits of flow - (Hydraulics 101) detrital heavy mineral concentration can be expected to reflect the mechanical energy applied, and some sort of distance/grade relationship is plausible. (The Carbon Leader gold mineralization is another matter, but if the algae mats acted as chemical traps and there was some difference in total flow (volume) from a 'channel' axis across the mats, one could expect to see a similar distribution of values, but the geological controls and the difference in depositional environment must be considered.) Statistics, in my experience, may be applicable in ore reserve estimation, (and will solve many problems if properly applied) providing they are used with due reference to the geological controls on deposition. And this applies to mechanical and chemical mineralization systems equally. The chemical systems are usually the more difficult to deal with. Jim - Original Message - From: Isobel Clark To: Stephen Henley Cc: AI Geostats mailing list Sent: Wednesday, February 08, 2006 10:07 AM Subject: [ai-geostats] Re: Geostats Scam? And don't forget the 27 page article by Philip Watson "Matheronian geostatistics - Quo Vadis?" in Mathematical Geology, vol 18, pp 93-117. 24 pages on what a confidence trick geostatistics is. There are response letters in that volume and later volumes from members of the geostatistical community. A wonderful example of neither side listening. Bear in mind when you read this article that it was not refereed before publication. In fact, this is a very good paper to illustrate the enormous difference which can occur when you approach a problem from a completely different direction. What baffled me for a long time is that their argument is that where you have more data, you have
FW: [ai-geostats] Re: Geostats Scam?
Title: Message 4 times ! I guess my forwarded mail should be read by the rest of the list as well to avoid similar situations in the future. Thanks Gregoire From: Gregoire Dubois [mailto:[EMAIL PROTECTED] Sent: 09 February 2006 13:32To: 'Fran Manns'Subject: RE: [ai-geostats] Re: Geostats Scam? Fran, I have received your message 3 times! The ai-geostats mail server needs to redistribute your mail to more than 1000 people and it is not the only mailing list the server is hosting. So please wait at least a few hours before sending your message again or contact me if you think there are problems with your postings. Thank you for your cooperation Gregoire (moderator of ai-geostats) __ Gregoire Dubois (Ph.D.) European Commission (EC) Joint Research Centre (JRC) WWW: http://www.ai-geostats.org "The views expressed are purely those of the writer and may not in any circumstances be regarded as stating an official position of the European Commission." -Original Message-From: Fran Manns [mailto:[EMAIL PROTECTED] Sent: 09 February 2006 12:42To: AI Geostats mailing list; Isobel ClarkCc: J. E. TilsleySubject: Re: [ai-geostats] Re: Geostats Scam? Isobel, I keep in mind at all times that wonderful sentence in Clark (1979), "Systematic errors, be they sampling , analytical, or whatever, will not be picked up by geostatistics and will be transferred to any estimates produced." (p. 119) Isobel,this wisdomshould be included in the disclaimer of any geostatistical report. If one looks at the lead paper of the Australian Best Practices Volume (proper citation not available because I have misplaced thebook). More than 50% of gold deposits fail to achieve nameplate output in the first year of production due to grade shortfall (David Harquail, Graham Clow and and Australian masters thesis). Then things improve, not from statistics, but using fudge factors(mine call factor, cutting, whatever). Mike Armitage, Managing Director of SRK, is on record in the SRK newsletter stating that the predictability of geostatistics is no better today than at any time in the past. I took issue with Danie Krige in the SAJG for saying, in 2001, the framework of geostatistics included all the necessary elements and no further discoveries need be made. In my experience, the issue is sampling, splitting, analysis, and execution. By the time a geological sample gets to a 30 gram aliquot, the likelihood of that 30 grams representing 1,000,000 grams of rock is probably compromised about 50% of the time. So we respond, in ignorance,by taking thousands of samples. In my opinion, 33 samples will suffice in am stope, giving two extra sample for more confidence Need to take large enough samples to be representative though. Got to avoid the systematic error of not having a representative sample for the region, deposit, stope, etc. I cringe when I see geostatistics applied to ground water projects or remediation projects, or astrophysics. Ask yourself whether asteroid size distribution as sampled mightsuffer a 'nugget effect'. Francis T. Manns, Ph.D., P.Geo. (Ont) Artesian Geological Research Toronto, Ontario And the following sense from Jim Tilsley also need to be integrated Fran, Questioning geo-stats is an advancement in understanding. This is good for everyone and everything involved. The point most overlooked in the 'equation' is the first half of the term. GEO! I, as you know, have always objected to statistics being the main focus. FIRST do the geology. Then we may find that some sort of statistical treatment can be applied rationally. As we have discussed before on many occasions, Kreiging works wonderfully on mature gold placers of the Wits. The trouble comes in when attempts are made to apply it to another type of mineralized zone, one that has not been deposited under the same energy regime as the Wits. There can be a relationship between grade - a parameter fraught with difficulties in the details - and relative position in respect to another grade, only when there is some sort of energy gradient that ties the two together - as in the paleo-placers for which the approach was developed. Since the energy budget correlates with the distance from the centre of the channel, decreasing toward the limits of flow - (Hydraulics 101) detrital heavy mineral concentration can be expected to reflect the mechanical energy applied, and some sort of distance/grade relationship is plausible. (The Carbon Leader gold mineralization is another matter, but if the algae mats acted as chemical traps and there was some difference in total flow (volume) from a 'channel' axis across the mats, one could expect to see a similar distribution of values,
Re: [ai-geostats] Re: Geostats Scam?
Francis Mann et al, This is a very interesting discussion, with several interesting and valid points of view. I aggree with most of them. Here are some additional comments from a mining geologist.. As one of my professors (F.F Osborne, petrology) repeated a few times when he felt that we were slow to understand : Rocks are geological bodies that occur in the field. Ore bodies also only occur in the field, and they also three dimensions and limits, all to be determined along with their composition. I wish all professors of mining geostatistics used similar statements in their lectures occasionally. Geology is a considerable part of determining the limits of orebodies! Actually, I feel we are going.backwards. In the past few years, thanks to NI 43-101 in Canada (and some other similar texts in other countries), and to loose implementation, we find that less and less discrite information on drill hole spacing(s) and regularity (or absence thereof) is provided. Feasibility and pre-feasibility studies are as bad as scoping studies in this regard. This is a major information shortcoming not only for the geologists that will be responsible for the final delineation and extraction of that material, but for the various people that have to appraise that information for technical, investment or other purposes, given the nature of orebodies. Another major information shortcoming that is tolerated by regulators, despite texts to the contrary, is systematically reporting measured resources and indicated resources together. How can the investing public, or even an independent consultant, find out that only 20% of the total is measured resources and 80 % is indicated resources, for instance. Current regulations and practice also allow much generous reporting of inferred resources as well as their use in pre-feasibility study and feasibility if closely associated with the measured and indicated categories. In spite of the much lower level of delineation, hence precision, both grade and tonnage are reported with the same number of significant figures ! ! !. These are matters of concern professional geostatisticians as well as to professors of geostatistics. Marcel Vallée Eng., Geo. = Géoconseil M. Vallée Inc. 706 Routhier St Québec, Québec Canada G1X 3J9 Tel: (1) 418 652-3497 Email: [EMAIL PROTECTED] = Fran Manns wrote: Isobel et al, I keep in mind at all times that wonderful sentence in Clark (1979), Systematic errors, be they sampling , analytical, or whatever, will /not/ be picked up by geostatistics and will be transferred to any estimates produced. (p. 119) Isobel, this wisdom should be included in the disclaimer of any geostatistical report. If one looks at the lead paper of the Australian Best Practices Volume (proper citation not available because I have misplaced the book). More than 50% of gold deposits fail to achieve nameplate output in the first year of production due to grade shortfall (David Harquail, Graham Clow and and Australian masters thesis). Then things improve, not from statistics, but using fudge factors(mine call factor, cutting, whatever). Mike Armitage, Managing Director of SRK, is on record in the SRK newsletter stating that the predictability of geostatistics is no better today than at any time in the past. I took issue with Danie Krige in the SAJG for saying, in 2001, the framework of geostatistics included all the necessary elements and no further discoveries need be made. In my experience, the issue is sampling, splitting, analysis, and execution. By the time a geological sample gets to a 30 gram aliquot, the likelihood of that 30 grams representing 1,000,000 grams of rock is probably compromised about 50% of the time. So we respond, in ignorance, by taking thousands of samples. In my opinion, 33 samples will suffice in am stope, giving two extra sample for more confidence. ... Need to take large enough samples to be representative though. Got to avoid the systematic error of not having a representative sample for the region, deposit, stope, etc. I cringe when I see geostatistics applied to ground water projects or remediation projects, or astrophysics. Ask yourself whether asteroid size distribution as sampled might suffer a 'nugget effect'. Francis T. Manns, Ph.D., P.Geo. (Ont) Artesian Geological Research Toronto, Ontario And the following sense from Jim Tilsley also need to be integrated *Fran,* Questioning geo-stats is an advancement in understanding. This is good for everyone and everything involved. The point most overlooked in the 'equation' is the first half of the term. GEO! I, as you know, have always objected to statistics being the main focus. FIRST do the geology. Then we may find that some sort of statistical treatment can be applied rationally. As we have discussed before on many
Re: [ai-geostats] Re: Geostats Scam?
Marcel -
I couldn't agree more.
As someone who has worked for many years with the Russian as well as the
western system of reserves/resource classification, it is my experience that
the Russian system - being more prescriptive - frequently yields better
resource estimates than the western, despite its reliance on 'antiquated'
polygonal and polyhedral computational methods. Unfortunately, in recent
years the pressures from western companies have led to similar problems to
those you describe, such as lumping together Russian C2+P1 category
resources. Within each category, for each type of deposit, the intensity and
type of work done (drill-hole spacing for example) is well defined: but as
soon as you combine categories this information is lost.
There is another reason that the Russian system, operated mainly by
geologists trained in the Soviet system, yields better quality estimates.
This is quite frankly political. There was, in Soviet times, pressure at the
individual mine management level to minimise stated reserves on which
production quotas were based - in order to make it easier to achieve the
quotas and to receive bonuses for exceeding quotas. This balanced the
geologists' natural optimism to produce fairly reliable estimates.
In the western system, on the other hand, there is often pressure on
consultants from clients who wish to maximise their stated reserves and
resources in order to boost their share price. In one blatant case where I
was personally involved, my own estimate - which was smaller than it might
otherwise have been (and smaller than the client expected) - because I took
into account geological zonation of the deposit - was rejected, and another
consultant was asked to do a new model using a particular flavour of
geostatistics (specified by the client) and ignoring the geological zoning.
Needless to say the second consultant's estimates came out substantially
higher and were the fgures that were published. I do not know the effect on
the client company's share price at the time, but I doubt if it was negative
! However, there is some justice. Not too long after that, the client's
entire board of directors were replaced. Unfortunately mining has still not
started on that deposit, so it remains to be seen whose model was closer to
the truth.
As for the use of inferred resources - the Russian system has three
categories P1, P2, and P3 of prognostic resources. Of these only P1 has
any counterpart in the west ('inferred') - the other two reflect different
even more rarefied degrees of geo-philosophy and wishful thinking. There is
perhaps just one justification for either the western or the Russian
categories for inferred or prognostic resources, and that is to indicate the
possibility - NO MORE - that further detailed exploration work might
establish something worth mining. In my view none of these categories should
have any place in the main body of a formal feasibility or pre-feasibility
report or any market statement based on it.
What is even worse, though, in my opinion, is the balds statement in company
announcements of individual drill-hole intersections: e.g. 15 metres at 5
grams per tonne. It just takes three or four of these, and investors, many
of whom should know better, will start joining the dots and doing their own
calculations. The answers they get are invariably over-optimistic (just as
the company intended) and the share price gets an unjustified boost as a
result. I think the reporting of isolated exploration results like this
should simply be outlawed.
- Steve
- Original Message -
From: Marcel Vallée [EMAIL PROTECTED]
To: Fran Manns [EMAIL PROTECTED]
Cc: Stephen Henley [EMAIL PROTECTED]; Isobel Clark
[EMAIL PROTECTED]; J. E. Tilsley [EMAIL PROTECTED]; AI
Geostats mailing list ai-geostats@unil.ch
Sent: Thursday, February 09, 2006 3:15 PM
Subject: Re: [ai-geostats] Re: Geostats Scam?
Francis Mann et al,
This is a very interesting discussion, with several interesting and
valid points of view. I aggree with most of them. Here are some
additional comments from a mining geologist..
As one of my professors (F.F Osborne, petrology) repeated a few times
when he felt that we were slow to understand : Rocks are geological
bodies that occur in the field. Ore bodies also only occur in the
field, and they also three dimensions and limits, all to be determined
along with their composition. I wish all professors of mining
geostatistics used similar statements in their lectures occasionally.
Geology is a considerable part of determining the limits of orebodies!
Actually, I feel we are going.backwards. In the past few years, thanks
to NI 43-101 in Canada (and some other similar texts in other
countries), and to loose implementation, we find that less and less
discrite information on drill hole spacing(s) and regularity (or absence
thereof) is provided. Feasibility and pre-feasibility studies are as
bad as
Re:[ai-geostats] Where's the variance?
I will suggest Jan to read some basic geostatistics theory, and more particularly on stationary random functions. But, Jan, you are all right, geostatistics is a particular case of mathematical statistics. Please, find the Matheron thesis and read it. De: "JW" [EMAIL PROTECTED] Para: ai-geostats@unil.ch Cópia: Data: Thu, 9 Feb 2006 08:52:06 -0800 Assunto: [ai-geostats] Where's the variance? Hello List, All I really want to know is what happened to the variance of a single distance-weighted average whenthe latter metamorphosedinto an honorifickriged estimate and the kriging variance of a SET of kriged estimates became a cornerstone of geostatistics.Readers should try to figure out what would happen to geostatistics if each and every kriged estimate does indeed have its own variance? I submit that geostatistics would simply mutate intomathematical statistics! Coulda first generation geostatisticianplease explain why the variance of a single distance-weighted average-cum-kriged estimatewas dismissed,ignored or otherwise lost? Kind regards, Jan W Merks * By using the ai-geostats mailing list you agree to follow its rules ( see http://www.ai-geostats.org/help_ai-geostats.htm ) * To unsubscribe to ai-geostats, send the following in the subject or in the body (plain text format) of an email message to [EMAIL PROTECTED] Signoff ai-geostats
