73235 (83) Aphanitic Impact Melt Breccia
Collection:
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Fact sheet

73235 (83) Aphanitic Impact Melt Breccia

73235 has a fine-grained aphanitic matrix and is trace-element-enriched, with a bulk composition similar to that of 73215 and 73217. It has a dense, aphanitic melt groundmass with seriate clast distribution. The groundmass consists mainly of plagioclase, pyroxene, opaque minerals and rare pink pleonaste spinel. Zircon is also reported in a unique clast from this sample (in section 82). Lithic clasts include granoblastic feldspathic impactites with a variety of grain sizes, shocked anorthosites, and cataclasized troctolites and norites. Many lithic clasts are strung out as schlieren within the dense matrix. Rotation 1 shows what is thought to be a recrystallised plagioclase clast. Rotation 2 focuses on a region of clast-laden melt.

The sample weighed 878.3 grams before analysis and has been dated at 3.96 ± 0.04 billion years (Ar/Ar).

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

About this collection

Apollo 17, the final manned landing mission, had two objectives: to obtain samples of ancient rocks from the lunar highlands and to look for evidence of younger volcanic activity on the valley floor.

This small Collection contains material deriving from both periods, including igneous rocks around 4.3 billion years old from the lunar highlands as well as younger volcanic samples dating from about 3.6 billion years ago.

Apollo 17 was launched on 7 December 1972.

Sample details

Collection: Apollo 17
Type
metamorphic
Rock-forming mineral
olivine
pyroxene
plagioclase
feldspar
Accessory minerals
spinel
ilmenite
metallic iron
zircon
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: