Sandstone, Tuff
Sandstone and tuff are rocks classified as sedimentary rocks. Clastic rocks include clastic rocks, chemical sedimentary rocks, and biological sedimentary rocks, and their properties change depending on grain size and the formation process.
Sedimentary rocks with diverse patterns and textures, also traded as ornamental stones.
Basic Information
| English Name | Sandstone, Tuff |
|---|---|
| Japanese Name | Sandstone, Tuff |
| Chemical Formula | — (Indeterminate as it is a rock) |
| Classification | Sedimentary rock |
| Hardness | 4–7 |
| Specific Gravity | 2.5–2.9 |
| Transparency | Opaque |
Characteristics & Variations
- Grain Size Reference: Sandstone is formed from sand (2–1/16 mm), mudstone from mud (1/16–1/256 mm), and tuff is volcanic ash equivalent to gravel, consolidated by diagenesis.
- Silicified Rock: Found in mudstone, sandstone, and tuff, these are rocks that have been hardened by the infiltration of high levels of silica.
- Novaculite: A type of flint, sometimes referred to as "dense sandstone" due to its fine-grained structure.
- Mookaite: Found in the Mooka Station region of Western Australia. Volcanic ash that has been silicified and hardened.
- Landscape Stone: The Liesegang phenomenon creates complex striped patterns, resulting in imagery resembling landscapes or geometric designs.
Trade Names & Treatments
Trade/Commercial Names: Picture Jasper: Technically, silicified picture sandstone.
Treatments: Dyeing and impregnation (porous stones may be dyed or resin-impregnated to improve porosity and polishability). Picture stones are sometimes painted to enhance or fill in missing areas of the pattern.
Notes: Even if called "Picture Jasper," it is often not true Jasper.
Note: Porous specimens are susceptible to the effects of dyeing and impregnation, and their appearance may change with cleaning or re-polishing.