updated 10/07
| Metallic | H<2.5 | H 2.5 to 3.5 | H 3.5 to 5.5 | H >5.5 | Glossary | Tests | Index |
| Rock Summary | Igneous | Sedimentary | Metamorphic |
| General Rock Type | Texture
- ave. size of minerals |
General color and/or composition - Miscellaneous observations | Rock Name | |
IGNEOUS
|
Fine grained Extrusive, volcanic |
Felsic - Light colored | Rhyolite | |
| Intermediate | Andesite | |||
| Mafic - Dark colored | Basalt | |||
Medium grained Dikes, sills, etc. |
Felsic - Light colored | - - - - - - | ||
| Intermediate | Dacite | |||
| Mafic - Dark colored | Diabase | |||
Coarse grained Generally intrusive |
Felsic - Light colored | Granite | ||
| Intermediate | Diorite | |||
| Mafic - Dark colored | Gabbro | |||
| Ultramafic | Peridotite | |||
| Glassy | Dark to black - felsic (DOES NOT follow normal color index) |
Obsidian | ||
| Frothy | Felsic - Light colored | Pumice | ||
| Mafic - Dark colored | Scoria | |||
SEDIMENTARY
|
Coarse Fragments | Rounded clasts | Conglomerate | |
| Angular clasts | Breccia | |||
| Sand sized fragments | Clean quartz (w/feldspar?) | Sandstone | ||
| Dirty w/rock fragments & clay | Graywacke | |||
| Fine grained - cannot see individual clasts | Nonfoliated, "clay the size" | Siltstone | ||
| Foliated, "clay the mineral" | Shale | |||
| Chemical - fine grain | Soft - passes fizz test | Limestone | ||
| Hard - fails fizz test | Chert | |||
| Fossiliferous | Mostly shell fragments | Coquina | ||
METAMORPHIC
|
F O L I A T E D |
Very fine grained-no visible minerals | Dull - passes "tink test" | Slate |
| Foliated, shiny due to increased size of micaceous minerals (almost see them) | Phyllite | |||
| Medium to coarse grain | Individual mineral grains visible. Major mineral(s) included as name modifiers | Schist (ex. Mica Schist) |
||
| Color banded | Alternating layers of light (felsic) and dark (mafic) minerals |
Gneiss | ||
| Distinct layering - often highly folded and contorted | Alternating layers of felsic igneous rock (light) and mafic gneiss (dark) | Migmatite | ||
| Non-foliated, with non-oriented grains |
Soft - passes fizz test | Marble | ||
| Hard - fails fizz test | Quartzite | |||
|
Interlocking hornblende crystals |
Amphibolite | |||
| Metallic | H<2.5 | H 2.5 to 3.5 | H 3.5 to 5.5 | H >5.5 | Glossary | Tests | Index |
| Rock Summary | Igneous | Sedimentary | Metamorphic |
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