12031 (7) - Pigeonite basalt
Collection:
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Fact sheet

12031 (7) - Pigeonite basalt

This interesting rock is not well studied, nor characterized. 12031 is a coarse-grained (~2 mm), equigranular rock with a variable texture. Graphic intergrowths of pyroxene and plagioclase give way to a more granular, gabbroic texture. Elongated and externally skeletal ilmenite, tridymite laths and interstitial cristobalite constitute the rest of the rock. Magnesian olivine and Cr-spinel are absent and pyroxenes are neither lath-shaped nor porphyritic. Plagioclase occurs as large, anhedral, poikilitic grains with prominent and complicated twinning. Groundmass phases are remarkably coarse-grained. Troilite is associated with phosphate at the junction of pyroxene and pyroxferroite. At the junction, pyroxferroite breaks down to fayalite, cristobalite and Fe-rich pyroxene in wormy intergrowths.

The sample weighed 185 grams before analysis and is 3.23±0.07 billion years old (Rb-Sr).

Deterioration of the embedding resin has resulted in the growth of colourful crystallites around the thin section.

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

About this collection

Apollo 12 returned 34 kilograms of samples, including 45 rocks, samples of lunar 'soil', and several core tubes that included material from as much as 40 centimetres below the lunar surface.

Apollo 12 rocks were almost all basalts, with only two breccias in the returned samples. The basalts at the Apollo 12 site formed 3.1 to 3.3 billion years ago, roughly 500 million years later than the Apollo 11 basalts. Overall, there is much less of the element titanium in the Apollo 12 samples than in the Apollo 11 samples, which explains the more reddish colour of this region. The differences in age and chemical composition between the Apollo 11 and Apollo 12 samples demonstrate that mare volcanism did not occur as a single, Moon-wide melting event.

Apollo 12 was launched on 14 November 1969.

Sample details

Collection: Apollo 12
Type
igneous
Rock-forming mineral
pyroxene
plagioclase
feldspar
Accessory minerals
ilmenite
troilite
pyroxferroite
fayalite
tridymite
cristobalite
phosphate
Category guide  
Category Guide
Title
Refers to any word or phrase that appears in the individual rock names. Names are generally descriptive; they allow users to search for broad terms like ‘granite’ as well as more specific names such as ‘breccia’. However, the adjacent descriptions of the specimens captures a wider range of general words and phrases and is a more powerful search tool.
Description
Refers to any word or phrase that appears anywhere in the descriptions of the specimens
Accessory minerals
Minerals that occur in very low abundance in a rock. They are usually not visible with the naked eye and contribute perhapssver, they often dominate the rare elements such as platinum group metals.
Rock-forming minerals
Minerals that make up the bulk of all rock samples and are also the ones used in rock classi?cation.
Timescale
Selecting one or more period, for example 'Jurassic'.
Theme
A term used to group together related samples that are not already gathered into a single Collection. For instance, there is a ‘SW England granites’ theme that includes such rock types as granite, hydrothermal breccia, skarn and vein samples.
Category
A general term used to label a rock sample. It is a useful way of grouping similar samples throughout a collection. Category names are often, but not exclusively, common rock names (e.g. granite, basalt, dolerite, gabbro, greisen, skarn, gneiss, amphibolite, limestone, sandstone).
Owner
The owner of the sample that appears in the collection. For example, NASA owns all the samples that appear in the Moon Rocks collection
We would like to thank the following for the use of this sample: