12051 (55) - Ilmenite basalt
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Fact sheet
Description: 

12051 is a medium-grained porphyritic basalt characterized by subhedral to anhedral phenocrysts of pyroxene (up to 10 mm) set in a subophitic matrix consisting of plagioclase laths (0.02-1 mm) and rare plagioclase anhedra (0.2 to 0.3 mm) intergrown with equant pyroxene crystals (0.2 to 1 mm) and rounded laths of ilmenite (0.3 to 1 mm). Ilmenite laths commonly cut across the silicates. Mesostasis includes glass, troilite, metallic iron, cristobalite and trace tranquillityite. The medium-grained equigranular texture consisting of lath-shaped plagioclase intergrown with equant to slightly elongate pyroxene is suggestive of coetectic crystallization of a homogeneous lava. No olivine phenocrysts have been reported. Elongate ilmenite and small segregations of “symplectoid mesostasis” are common features. Residual glass with high silica and high potassium is found interstitially and is associated with K-feldspar, fluorapatite, whitlockite and baddeleyite.

The sample weighed 1660 grams before analysis and is 3.15 to 3.5 billion years old (Rb-Sr and Ar/Ar).

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

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Not known
Ma = Millions of years ago
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igneous
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