12039 (45) - Pigeonite basalt
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Fact sheet
Description: 

12039 is a coarse grained porphyritic basalt which consists of pyroxene phenocrysts (0.8 to 4 mm), some of which are mantled by pyroxferroite, set in a matrix of intergrown plagioclase crystals, anhedral pyroxene, rounded laths of ilmenite and euhedral laths of tridymite (0.05 to 1 mm). Long needles of ilmenite and tridymite cut across plagioclase and pyroxene. Many of the clinopyroxene crystals show optical zonation from very light tan interiors (augite) to dark tan (ferroaugite) to reddish-brown (ferrohedenbergite) with an abrupt change to light yellow-green borders (pyroxferroite). Ilmenite is the major opaque phase and is intergrown with ulvöspinel. Tranquillityite, troilite, cristobalite and metallic iron are present in the groundmass.

The sample weighed 255 grams before analysis and is 3.2 billion years old.

Further details of this and other Apollo samples are here: http://curator.jsc.nasa.gov/lunar/

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Ma = Millions of years ago
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igneous
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