Other oxides
Section M 5.2.4.
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Other Oxides

All of these oxides are described by NASA as occuring with trace abundances only.


This is titanium oxide of composition TiO2, and is usually found associated with ilmenite. Most commonly, it is due to the reduction of ilmenite and/or armalcolite. In this association, it often contains Nd, Cr, Ta, and lanthanide elements. Colour is typically reddish-brown, but it may be black, violet, yellow or green. Typically yellow-red/brown in thin section. Density is 4.2-5.5 g/cm3. Rutile is insoluble in acids, but is decomposed by alkali carbonate fusion. Synthetic rutile has a dispersion much higher than diamond (B-G ~ 0.3) and is used as a germstone.


This is of the formula ZrO4 and is thought to be due to meteoritic contamination which has been incorporated into the original melts.


Also known as zirconolite, this has the formula CuZrTi2O7.


This has the formula Al2O3. This might be a contamination product, and may not be indigenous to the Moon. Density is 4 g/cm3, and it is insoluble in all acids. It is notably hard (9), resulting in abnormally high relief in thin section.


This is of the formula Fe2O3 - a common Fe ore on the Earth. This might be a contamination product, and not be indigenous to the Moon. Terrestrially, hematite is rare in igneous rocks, but common in metamorphic and sedimentary rocks. It is the most common cause of red colouration in sedimentary rocks.


This is of the formula Fe3O4, and is classified as a spinel due to its crystal structure. Density is 5.2 g/cm3. Magnetite is black, and is often soluble in HCl. See the section on spinels for further information.


This is formula FeO(OH), and as such is not strictly an oxide. The NASA Handbook of Lunar Materials lists this as a possible contamination product, but the Lunar Sourcebook goes into more detail. Goethite has been found in rocks from every Apollo mission, and is often described as "rust". It has been shown that akaganeite (beta-FeOOH) is due to terrestrial water vapour contamination, causing the oxidation of lawrencite (FeCl2) [Taylor et al 1973]. Hence there is still no evidence for indigenous water on the Moon.

Terrestrially, goethite occurs primarily as a weathering product. Density is approxiumate 4.3 g/cm3. Colours vary from yellow through orange to red. Soluble in HCl, and dehydrates to alpha-Fe2O3.


Taylor LA, Mao HK, Bell PM (1973) "Rust" in the Apollo 16 Rocks. Proc. Lunar Sci. conf. 4th, pp 829-839.

Other oxides

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