Dear fernando, I don't know too much about the radio side of quartz production, but it was needed during the war to make oscillators for the radio industry (and military, of course). These plates must be cut at a highly specific angle from a certain part of the crystal. Problem is, that many quartz crystals are twinned, that is, they are really two crystals growing about a common plane (as opposed to two crystals which by chance intersect each other in a random growth). Sometimes this is self evident (if you know what to look for), but often ordinary quartz crystals show little sign of their being two individuals (they come in right and left handed forms, like gloves). Twinned crystals are of no use for oscillator plates. Hence it was then necessary to mine an awful lot of quartz in order to be able to cut the plate, which must be perfect. There was probably an awful lot of waste. Perhaps at about that time, it became possible to grow synthetic crystals, but these need a seed plate which is also untwinned. Having a synthetic crystal is good because it can then be cut into many plates for oscillators, whereas only 1 plate is likely to come from a natural quartz crystal. I suppose that would depress the price of natural quartz, as the demand largely disappeared. Brazil has been a major supplier of quartz (and beryl, tourmaline, topaz......too many to mention!), and for the mineral specimen market, it still is. If you have access to cutting and tumbling machinery, maybe you could even make your own sphere, from a crystal. That would really be starting from scratch! Clear quartz is the most common variety, smoky, amethystine, are next, and rose quartz after that. Yellow (citrine) quartz is not very common, and blue is pretty well unknown in nature (but I've seen a superb synthetic example), except for some crystals with natural inclusions inside. That would make them more expensive on the specimen market. I hope this helps explain what you (don't) remember from the 'good old days'.
Regards Peter Tandy At 09:29 AM 4/20/99 +0200, you wrote: >Peter Tandy wrote: > >> Dear les, and everyone, >> >> In the Natonal collection of minerals in London, we have a superb QUARTZ >> sphere which should make an excellent sunshine recorder, and such spheres >> are available on the mineral market, mainly for the 'crystal healing' >> brigade. however, being a natural substance, quartz is often shot through >> with imperfections, and the possibility of finding a clear one is less >> likely (but not impossible). As an aside, we also have a magnificent >> CALCITE sphere which has strong double refraction (so two images of an >> objecr beneath it are seen. Food for thought.....????? > >Now that you've mentioned it, I rember good old days -- how could >I have forgoten them? -- when quartz was expensive. My home town >has a lot of quartz. During the World Word II many people made a >fortune with quartz. In my youth I was told the United States >used to import tons and tons of high quality quartz. I still don't why. >They certainly did not need that much quartz to build radios :-) > >But the fact is, by the end of the fifities there was a revival in the >quartz mining. A little while after that quartz became so inexpensive >that mining it did not pay off anymore. > >People started making all kind of quartz trinkets. Among them >some nice spheres. As of late I don't have seen them very often. >Perhaps just because I have not been paying attention. I'll double >check next time I go there for a visit. > >If they still exist, they certainly are vey high quality. As I can remember >it, >they only used the best quality quartz. Any imperfection would >render it useless. > >By the way, can anyone there confirm if in the forties quartz was more >valueable because of the war? If that was the case, why? > >- fernando > >PS - There was a variety of prices. crystal-clear quartz was the cheapest. >Colored quartz was more expensive, the price depending on the color >(bluish, redish, greyish...) - but all of these come from my early >childhood, when memory and fantasy are almost the same... > > >-- >Fernando Cabral Padrao iX Sistemas Abertos >mailto:[EMAIL PROTECTED] http://www.pix.com.br > mailto:[EMAIL PROTECTED] >Fone: +55 61 321-2433 Fax: +55 61 225-3082 >15º 45' 04.9" S 47º 49' 58.6" W >19º 37' 57.0" S 45º 17' 13.6" W > > > >
