15555 (256) Olivine Basalt
Collection:
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Fact sheet

15555 (256) Olivine Basalt

15555 (called “Great Scott”, after the collector Dave Scott) is one of the largest samples returned from the moon and is representative of the basaltic samples found on the mare surface at Apollo 15. The bulk composition of 15555 is thought to represent that of a primitive volcanic liquid. It contains olivine and pyroxene phenocrysts and has a sub-ophitic, basaltic texture. Two generations of olivine are present. Both olivine and pyroxene crystals are chemically zoned. There is little evidence for shock in the minerals. Accessory minerals include cristobalite, ilmenite, ulvospinel, chromite, troilite and metallic iron. An unidentified Zr-Ti-Fe mineral (“phase Y”) has also been reported.

The sample weighed 9614 grams before analysis. It has been dated at 3.33±0.05 billion years (Ar/Ar).

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

Additional images
About this collection

The Apollo 15 landing site was in the Apennine Highlands, and close to Hadley Rille — a long, narrow winding valley. Approximately 76 kg of lunar material, including soil, rock, core-tube and deep-core samples, were returned to Earth.

This mission was the first flight of the Lunar Roving Vehicle which allowed the astronauts to venture further from the Lunar Module than in previous missions. During three periods of extravehicular activity, or EVA, on July 31st, and August 1st and 2nd, Scott and Irwin completed a record 18 hours, 37 minutes of exploration, travelling 17.5 miles, in the first car that humans had ever driven on the Moon.

Apollo 15 was launched on 26 July 1971.

Sample details

Collection: Apollo 15
Type
igneous
Rock-forming mineral
olivine
pyroxene
plagioclase
feldspar
Accessory minerals
cristobalite
ilmenite
ulvospinel
chromite
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: