12051 (55) - Ilmenite basalt
Collection:
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Fact sheet

12051 (55) - Ilmenite basalt

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/

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
ilmenite
Accessory minerals
k-feldspar
cristobalite
chromite
fluroapatite
whitlockite
baddeleyite
tranquillityite
troilite
metallic iron
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: