| Id | Identification Type | Name | Description | Distinguishing Features | Tags |
|---|---|---|---|---|---|
| 135 | Mineral | Inclusion | Distinct mineral or fluid phases incorporated within the crystalline structure of a surrounding host mineral grain, often the result of elemental incompatibilities in igneous or metamorphic processes. In smear slides, typically recognized as optically distinct minerals with different birefringence, optical extinction angles, and/or relief from a surrounding, optically unitary, mineral grain. | ||
| 14 | Mineral | Iron (Hydr)oxides, Non-opaque (Hematite/Limonite) | Non-opaque iron oxides, hydroxides, and oxyhydroxides including hematite (which may also occur as opaque grains) and limonite (actually a mixture of minerals including goethite). Red to brown; limonite yellower. High relief. May occur as granular aggregates, scales, either translucent or transparent. May be isotropic or show low-order birefringence.
Hematite is red to brown, transparent to opaque. Red-brown in reflected light. Hematite has high birefringence, but may not be observable due to deep color of grains. Some hematite grains may be noncrystalline and thus isotropic. Irregularly shaped flakes and earthy or somewhat fibrous particles. High relief. Hematite occurs as detrital or authigenic/diagenetic grains. |
Translucent
Transparent Granular |
red brown yellow |
| 6 | Mineral | Iron Oxides, Opaque (e.g., magnetite) | Fully opaque where visible by light microscopy. In coarser, sorted lacustrine sediment, cubic, faceted, or irregularly blocky grains may occur in association with other high-density minerals. May be distinguished from pyrite and other sulfides by grey color under oblique reflected light. Biomineralized magnetite produced by magnetotactic bacteria is widespread in sedimentary environments, but normally in a sub-micron size class well below that of grains discerned in smear slides. | heavy-mineral |
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