Hi Bernd and all,
Agreed, there is accessory amounts of olivine in mesosiderites but
these are very low amounts so the olivine seem to be mostly absent in
the formation. Most likely the amounts found were mixed in formation.
This also explaines the green olivine crystal(s) found in some of
Martinez Rodrigo's specimens. Could these be from the pallasite
producing part of an asteroid?
Always appreciate your input Bernd and you are a treasure to this list!
--AL Mitterling
Quoting [email protected]:
AL kindly wrote:
"I believe there is an absence of olivine in mesosiderites."
Objection, Your Honor!
Norton O.R. (2002) The Cambridge Encyclopedia of Meteorites, p. 157:
"Accessory amounts of olivine are also present in mesosiderites"
"...the mineralogy of the silicate portion...is ...orthopyroxene and
plagioclase with minor amounts of olivine."
Norton O.R. (2008) Field Guide to Meteors and Meteorites, p.173:
a) Figure 8.10: "Estherville...Silicates include olivine, pyroxene,
and plagioclase..."
b) Figure 8.11: "Vaca Muerta...Like Estherville, it contains eucritic
pebbles and
many silicate inclusions..."
T.H. Burbine et al. (1996) Mantle material in the main belt:
Battered to bits (Meteoritics 31-5, 1996, 607-620, p. 609):
"Mesosiderites are stony-iron meteorites containing Ni-rich Fe metal
and mafic
silicates (Floran, 1978). The amount of metal has been found to vary from 17
to 80 wt% but is usually between 40 to 60% (Mason and Jarosewich, 1973). The
silicates are mainly orthopyroxene and plagioclase with lesser
amounts of other
silicates such as pigeonite and olivine (Floran, 1978)."
By the way, a few years ago, Martinez Rodrigo offered thin Vaca Muerta slices
with predominantly eucritic components and / or olivine crystals. Some of the
olivine-rich slices were cut so thinly that they were even
translucent when held
up against the light.
Best wishes,
Bernd
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