15387 (7) Picritic Basalt

Collection:

Apollo 15

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Fact sheet

15387 (7) Picritic Basalt

15385 and 15387 were collected as part of a rake sample. They were probably pieces of the same coarse, friable basalt. They are similar in texture, chemical composition and mineralogy. Olivine grains (Fo62) are large and rounded with abundant chromite inclusions (rotation 1). Some have melt inclusions. The relatively high Ca content of olivine in 15387 indicates that this is not a plutonic rock. The olivine probably has a cumulate origin. Pyroxene grains are large and euhedral and may also be of cumulate origin (rotation 2). 15385 and 15387 have abundant small, usually euhedral chromite or ulvospinel grains. They often form clusters and are commonly present in early olivine, but also in the groundmass. Ulvospinel is subhedral to anhedral and is present in some of the later-formed major minerals, but mainly in the groundmass. Some ulvospinel-ilmenite intergrowths are observed. Rock 15387 is similar to 15385, but has less chromite and more ulvospinel.

The sample weighed 2 grams before analysis. It has not been dated, although its companion 15385 is dated at 3.39±0.06 billion years (Ar/Ar).

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

About this collection

Apollo 15

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

ulvospinel

ilmenite

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

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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.