Posted on 04/20/2004 8:13:40 AM PDT by cogitator
Partly because I missed a week for various reasons, this week I offer something a bit different: fundamental to the practice of geology and mineralogy, but far different from pictures of volcanoes, geological formations, or remote-sensing from space. These are thin-sections; slices out of rocks viewed with a microscope (frequently with a polarizer to bring out remarkable and beautiful colors and patterns).
First up: I don't know what this is, but there's a lot in it!
Thin section from the Nakhla (Martian) meteorite, primarily pyroxene and feldspar:
Monzonite porphyry: there's a bit more information on this one: "This rock is holocrystalline, phaneritic, medium- to coarse-grained, hypidiomorphic-granular. All crystals are subhedral except pseudoleucite, carbonate, and opaque minerals, which are subhedral to anhedral. The following are present as phenocryst phases: biotite (1-3 mm) and phlogopite; acicular aegerine-augite (1-4 mm); titanaugite (1-4 mm); plagioclase (1-4 mm) is heavily altered to fine-grained phyllosilicates; potassium feldspar (1-4 mm); opaques (1< mm); carbonate (<1 mm); apatite (<.1 mm); sphene (.1 mm); analcite (<1 mm); pseudoleucite (1 mm) is present as a mass of subhedral nepheline and potassium feldspar crystals. Biotite was the phase dated."
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