... quality (porosity). The X-ray analysis also yields little or no information about rock components that do not have a definite crystalline structure. This includes mineraloids, such as kerogen, and amorphous silica, such as opal. Because of limitations due to magnification, the thin section cannot be used...

... would develop as an intermediate step between the two end minerals. Iron Oxides and Hydrous Oxides Hematite and the mineraloid limonite are the common forms resulting from oxidation or oxidation plus hydration of ferromagnesian minerals into clay sized particles. Two structurally different FeO'OH...

... Mixture of clay and silt Limestone Mixture of shells, coral, and other marine skeletons Non-clastic Sedimentary Rocks These sedimentary rocks occur when minerals/mineraloids are precipitated directly from water, or are concentrated by organic matter/life. These components have not been...

... and very low O/H substances have the greatest "geological timescale sta- bility". Same as under 2, as a first approximat- ion. Retigen of meteorites ? Inferred carbonaceous phase of comets 9 Terrestrial tucholites and allied organic mineraloids ? Carbonaceous complex of Kaba meteo- rite ? Hydrocarbon gases...