NWA 6871 - Ureilite Meteorite
Single stone, cut showing the interior
NWA 6871
Classification: Ureilite
Year found: April 2010
Country: Northwest Africa
TKW: 119 grams (one complete stone)
Northwest Africa 6871
(NWA 6871)
Classification: Ureilite
Physical characteristics:
A single
extremely hard, brown stone weighing 119 g and almost impossible to cut.
Small adamantine crystals of diamond were extracted from the stone by
Mr. Catterton.
Petrography:
Coarse-grained
aggregate of olivine and orthopyroxene with finer grained interstitial
regions containing opaque material, calcite and limonite. Some thin
calcite veinlets cross-cut the specimen. Both olivine and pyroxene are
completely recrystallized to aggregates of myriad tiny, polygonal
subgrains.
Geochemistry:
Olivine cores Fa19.4-20.0 (CaO=0.3 wt.%, Cr2O3=0.7 wt.%), rims Fa10.5; orthopyroxene Fs12.6-13.7Wo3.7-3.4.
Classification:
Achondrite
(ureilite). The very high shock experienced by this specimen (causing
complete recrystallization of silicates and evidently generation of
significant amounts of microdiamond) is unusual among ureilites.
| Mass (g): | 119 |
| Pieces: | 1 |
| Class: | Ureilite |
| Shock stage: | high |
| Weathering grade: | moderate |
| Fayalite (mol%): | 19.4-20.0; 10.5 |
| Ferrosilite (mol%): | 12.6-13.7 |
| Wollastonite (mol%): | 3.7-3.4 |
| Classifier: | A. Irving and S. Kuehner, UWS |
| Type spec mass (g): | 20 |
| Type spec location: | UWS |
| Main mass: | G. Catterton |
| Comments: | Submitted by A. Irving |
This may be one of the hardest ureilites that has ever been found. Cutting this was very tough and costly as it chewed through several blades.
Along the cut surface, you can actually feel objects (diamonds?) sticking out of the meteorite. I am not sure at this time what these are, but do know they are what is cutting into the saw blades. I suspect this is very high is diamond content.
UPDATE: "Ureilite NWA 6871 is unusual, because of the intensity of shock it evidently experienced: the silicate minerals (olivine and pyroxene) are entirely recrystallized to fine grained mosaics of subgrains, and any primary carbon would have been transformed into microdiamond by this process"
Here is the single stone prior to cutting.
18g
15g
8g
7g
5g
4g
3g
2g
Sub-gram and micros
