All of these silicates have been described as of trace concentrations
in the regolith, by NASA.
Zircon has the formula of ZrSiO4, but tends to concentrate REEs. It is
also noteworthy due to its usefulness in dating rocks. This is because
it is a refractory mineral which resists remelting and often
incorporates Hf, Th, U in its crystal structure. Hence it is well
suited to U-Pb dating (and is the basis of terrestrial "oldest crust"
rock dates). It has also been shown that their U-Pb systematics are
unaffected by meteor bombardment! Although rare, small, and difficult
to work with, lunar zircons have proved to be extremely important in
dating lunar samples - especially the very old highland material.
Zircons also tend to keep fission tracks (linear damage caused by
spontaneous fission of U atoms), and is hence also suited to fission
track dating methods.
The main source of lunar zircons are the rare high-silica "granitic"
rocks. Sample 15405 (breccia of quartz monzodiorite composition)
contained 0.6 vol% zircon.
However, most lunar zircons are found as isolated grains in soils and
breccias. This is due to the rarity of lunar granitic rocks, and the
durability of zircons. They have also been found in metamorphosed
basalt clasts - possibly due to the breakdown of original tranquillityite.
Density is in the range of 4.6-4.7 g/cm3 for fresh samples. Colors are
red/brown/yellow/grey/green. It is slowly attacked by hot concentrated
The crystal group is tetragonal.
This is the lunar iron analogue of pyroxmangite. Composition is (Mn, Fe)
although terrestrial pyroxmangite never has more than 25 % Fe : Mn.
Pyroxmangite is pinkish-lilac in color. Pyroxferroite is found in mare
basalts and Fe-rich basalts. Although produced artificially in the
lab, pyroxferroite (rather than pyroxmangite) has never been found on
The amphiboles are a complex group of minerals. On Earth they are
typically formed during metamorphism, or in some igneous rocks. They
can also survive the sedimentary cycle.
General composition is (Ca, Mg, Fe) (Si, Al)8 O22F although many
different substitutions are possible.
NASA list garnets as being possible contamination products and may not
be of indigenous lunar origin.
On Earth, garnets are surprisingly common, and are produced by
moderately high pressure metamorphism. Before everyone gets excited
that these might be mined for semi-precious gems to be shipped back to
Earth, it should be borne in mind that the majority of garnets on Earth
are worthless due to inclusions, fractures, or non-gem compositions. I,
myself, have seen hundreds if not thousands of garnets in thin section
- all have had inclusions in them. I have even picked moderate sized
samples (8mm or so) from cliffs in Scotland!
this mineral is named after the
Apollo 11 landing site. Density is 4.7 g/cm3.
This is found in lunar mare basalts where it forms small laths less
than 100µm long. It is often associated in small pockets with apatite
and pyroxferroite. These are the last minerals to crystallize.
It is semi-opaque and non-pleochroic. In transmitted light, it is
deep red, but is grey in reflected light. The deep red is due to the
high Ti content.
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