72559 (7) Granoblastic Impactite
We would like to thank the following for the use of this sample:
72559 is a rake sample with an annealed feldspathic impactite texture. It has been described as an impact melt derived from anorthositic & troctolitic material and as a recrystallized norite. 72559 contains 75% plagioclase feldspar, 15% olivine (rotation 1) and 10% orthopyroxene, with minor augite, Mg-Al spinel, chromite, armalcolite, ilmenite, zircon, K-feldspar, metallic iron and troilite. Larger grains of plagioclase and olivine are set in a finer-grained granoblastic groundmass made up of plagioclase, olivine and orthopyroxene (rotation 2). The recrystallized and annealed groundmass is distinguished by triple-junction grain boundaries and larger poikilitic orthopyroxene enclosing smaller plagioclase and olivine.
The sample weighed 27.8 grams before analysis and has not been dated.
Further details of this and other Apollo samples are here: http://curator.jsc.nasa.gov/lunar/
Ma = Millions of years ago
Rock forming mineral:
- mg-al spinel,
- metallic iron