61156 (26) Impact Melt Breccia
Collection:
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Fact sheet

61156 (26) Impact Melt Breccia

61156 is an impact melt rock with a high percentage of KREEP and has also been called “metaigneous”. The matrix of 61156 has a well-developed poikilitic texture, but the sample has a significant number of xenocrystic clasts of plagioclase-rich highland material (see rotation 1). It is a dense, fine-grained poikilitic rock with relatively large (1 mm) pyroxene grains that enclose small euhedral plagioclase crystals. The matrix includes areas of interlocking plagioclase, olivine, high-Ca pyroxene and K-rich patches. Other minerals found in the matrix include ilmenite, armalcolite, chromite, rutile, baddeleyite, metallic iron, apatite, whitlockite and troilite.

The sample weighed 58.46 grams before analysis and has been dated at 3.749±0.036 billion years (Ar/Ar).

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

About this collection

The Apollo 16 landing site was in the hilly region around Descartes crater in the lunar highlands. The landing spot was chosen to allow the astronauts to gather geologically older lunar material (Descartes Formation and the Cayley Formation) than the samples obtained in the first four landings, which were in or near lunar maria.

The mission lasted 11.1 days, with a stay on the lunar surface of 71 hours. The crew were on the lunar surface for 20.2 hours during which they traversed approximately 27 kilometers and collected approximately 96 kilograms of samples.

Apollo 16 was launched on 16 April 1972.

Sample details

Collection: Apollo 16
Type
metamorphic
Rock-forming mineral
plagioclase
feldspar
pyroxene
olivine
Accessory minerals
ilmenite
armalcolite
chromite
rutile
baddeleyite
metallic iron
apatite
whitlockite
troilite
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: