Shale
Rock made of clay minerals, quartz
Common
The most common sedimentary rock: hardened mud of clay flakes and silt that splits into thin sheets less than a centimetre thick. Usually grey; organic matter darkens it to black.
Rock
- Kind of rock
- Clastic sedimentary rock
- Rock family
- Sandstone, shale and clay
- Texture
- clastic (grains cemented together), fissile (splits into thin sheets)
- Also contains
- Calcite
- Deposits
- Ironstone beds
- How it forms
- Mud settles in quiet water; as it is buried, its clay flakes lie flat and the rock splits along them.
- Uses
- The parent rock of slate.
Crystallography
- Habits
- Foliated
Physical properties
- Luster
- Dull, Earthy
- Colors
- gray, dark gray, black
- Transparency
- Opaque
Geology
- Origins
- Sedimentary
- Geography
- worldwide
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- Shale. Wikipedia.
- C. R. Hallsworth, R. W. O’B. Knox, BGS Rock Classification Scheme, Volume 3: Classification of sediments and sedimentary rocks (Research Report RR 99-03). British Geological Survey, 1999.
Browse the Crystal Encyclopedia — MGS Toolbox