Goalpara meteorite, Goalpara District, Assam, Indiai

Regional Level Types
Goalpara meteorite	Meteorite Fall Location
Goalpara District	District
Assam	State
India	Country

Goalpara (India) [1868 Find] A single meteoritic 2.7 kg stone
Classification: Ureilite (Ca-poor achondrite)

A single stone of 2.7 kg was sent by the Rajah of Goalpara to the Calcutta Museum. Goalpara is now known as a ureilite. While by 2013 over 300 ureilite stones have been listed in the Meteoritical Society’s Database, most of them are quite small and/or have been recovered in the 21st Century. Goalpara is actually the most massive of the three known ureilites recovered in the 19th Century. Indeed, Goalpara was the most massive ureilites known before the recovery of the Kenna (New Mexico, USA) ureilite in 1972. Consequently, as small portions of Goalpara have been available in different museums, Goalpara has been around long enough to be the subject of several inquiries.
Ureilites are known for their curious amalgam of cumulate silicates (mostly olivine and pyroxene) mixed with elemental carbon. The carbon itself is always an enigmatic graphite-diamond mix . In Goalpara, four polymorphs of carbon are known (chaoite, diamond, graphite and lonsdaleite). The presence of Lonsdaleite, a hexagonal diamond-like polymorph, may indicate a directional pressure associated with impact shock. The ureilites also usually contain a number of minor opaque minerals. Metallic iron (kamacite) and iron sulfide (as troilite) are invariably present. The ureilites are particularly intriguing because their microscopic textures may have been due to both vapor condensation and to shock impact. Both the relative importance and the timing of these nebular and collisional processes does not appear to be a settled matter at this time.

References

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