15663 (11) Coarse Olivine Basalt
We would like to thank the following for the use of this sample:
15663 was collected together with other fragments (15633, 15641 and 15643) in a rake sample. They are grouped together because they are relatively coarse-grained samples of the abundant olivine normative Apollo 15 basalt clan. Most olivine grains are less than 1 mm; the larger ones contain silicate melt inclusions. Pyroxene grains are up to 2 mm and somewhat elongate. They are chemically zoned from pigeonite to Fe-rich augite (see rotation 2). Plagioclase grains up to 3mm, poikilitically enclose small pyroxene, otherwise intergrown with pyroxene. Chromite is found in pyroxene and is overgrown with ulvospinel when it is interstitial. Minor phases include cristobalite (see centre of rotation 1), fayalite, ilmenite, troilite, metallic iron and Fe-rich glass.
The sample weighed 10.5 grams before analysis and has been dated at 3.26 billion years (Ar/Ar).
Further details of this and other Apollo samples are here: http://curator.jsc.nasa.gov/lunar/
The mounting resin of this thin section has deteriorated over time and now contains clusters of colourful dendrites around the thin section.
Ma = Millions of years ago
Rock forming mineral:
- metallic iron