| Clastic Sedimentary Rocks | |||
|---|---|---|---|
| Grain Size | Rounding | Sorting | Rock Name |
| gravel coarse (> 2 mm) |
angular | poorly | breccia |
| rounded | poorly | conglomerate | |
| sand medium (0.0625 - 2 mm) |
variable | variable | sandstone |
| rounded to subangular | well to moderately | quartz arenite - >90% quartz | |
| subrounded to angular | well to moderately | arkose - >25% feldspar | |
| subangular to angular | moderately to poorly | graywacke - high % lithics, clay matrix | |
| silt fine (0.004 - 0.0625 mm) |
variable | well | siltstone |
| clay extra fine (< 0.004 mm) |
not visible | well | shale - breaks along bedding planes |
| mudstone - lacks bedding planes | |||
| claystone - pure mineral clay, very soft | |||
| Chemical Sedimentary Rocks | |||
|---|---|---|---|
| Mineral | Distinguishing Characteristics | Rock Name | Common Depositional Environment |
| calcite | softer than glass, reacts to HCl | limestone | warm shallow ocean |
| calcite | visible fossils, softer than glass, reacts to HCl | fossiliferous limestone | warm shallow ocean |
| dolomite | white to pink, softer than glass, reacts to HCl only when powdered | dolostone | saline lagoon |
| calcite | gray or brown, porous, reacts to HCl | travertine | evaporated spring or cave water |
| calcite | white, powdery, reacts to HCl | chalk | warm shallow ocean |
| microscopic quartz | conchoidal fracture | chert | deep ocean floor |
| microscopic quartz | red, conchoidal fracture | jasper | deep ocean floor |
| microscopic quartz | black, conchoidal fracture | flint | nodules in limestone |
| microscopic quartz | translucent, layered, conchoidal fracture | agate | nodules in volcanic rocks |
| microscopic quartz | white, powdery | diatomite | lakes in volcanic environments |
| carbon | black, soft, low density | coal | heavily vegetated swamp |
| halite | tastes like salt, cubic crystals and cleavage | rock salt | evaporating water body |
| gypsum | softer than fingernail | gypsum rock | evaporating water body |
Geology 101 - Introduction to Physical Geology
Basics Table--Sedimentary Rock Classification
Created by Ralph L. Dawes, Ph.D. and Cheryl D. Dawes, including figures unless otherwise noted
updated: 9/16/13
Basics Table--Sedimentary Rock Classification
Created by Ralph L. Dawes, Ph.D. and Cheryl D. Dawes, including figures unless otherwise noted
updated: 9/16/13
Unless otherwise specified, this work by Washington State Colleges is licensed under a Creative Commons Attribution 3.0 United States License.