SaU 008 Martian shergottite

Sayh al Uhaymir 008 is one of the several pairings with SaU 005. These pairings have a total weigh of about 25 pounds. It is a Martian basaltic shergottite of a type sometimes called olivine-phyric.

It is composed of olivine megacrysts in a finer grained groundmass of pigeonite and plagioclase. In these cross-polarized light (XPL) photos the large olivine crystals are brightly colored. The pigeonite, a pyroxene, shows bands of color representing shock induced twinning. Here, the plagioclase, a feldspar, has been shocked to the glass-like form called maskelynite and appears black in XPL. Note that opaque minerals and voids also appear black.

Other shock features are melt pockets and attendant vacuoles. Often melt cools very fast to a glass as obsidian does in some volcanic situations. In one pocket in this thin section the melt had time to crystallize into fine, fernlike forms.

Overview. Sample is 18mm long maximum dimension corner to corner. Thin section, cross-polarized light (XPL). SaU 008 Martian shergottite.

 

Olivine megacrysts in a finer grained groundmass of pigeonite and plagioclase. FOV = 3mm wide, XPL. SaU 008 Martian shergottite.

 

Olivine megacrysts in a finer grained groundmass of pigeonite and plagioclase. XPL. SaU 008 Martian shergottite.

 

Olivine megacryst in a finer grained groundmass of pigeonite and plagioclase. Note the oval opaque spot with fine radiating cracks above center. FOV = 3mm wide, XPL. SaU 008 Martian shergottite.

 

Spot with fine radiating cracks in large olivine crystal. FOV = 0.5mm wide, XPL. SaU 008 Martian shergottite.

 

Melt pocket with brownish recrystallized melt, black glassy solidified melt and oval void at top right, a vacuole. XPL. SaU 008 Martian shergottite.

 

Fernlike recrystallized melt. FOV = 0.4mm wide, XPL. SaU 008 Martian shergottite.

 

Thin section. SaU 008 Martian shergottite.

About the Author

John Kashuba
John is a natural history enthusiast living in Oregon.
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