Rudite
From Wikipedia, the free encyclopedia
Rudite is any sedimentary clastic rock with a grain size exceeding 2 mm (0.08 in)[1] such as conglomerates and breccias.
The term is used in the classification of clastic carbonatic limestones, although the granulometrically equivalent terms conglomerate and breccia are often used for limestone too.
Rudites mainly form by erosion of other rocks or turbiditic re-deposition of pebbles or already consolidated rocks. Some rudites contain rounded components and thus belong to the rock-category of conglomerates, others composed of angular fragments are called breccia. The interstices between the coarse grains are filled with a silicatic or carbonatic matrix. Rudites mostly appear as massive or crudely bedded rocks with a wide-spaced foliation and an irregular and wide-spaced cleavage.
Pettijohn [2] gives the following descriptive terms based on grain size, avoiding the use of terms such as clay or argillaceous which carry an implication of chemical composition. The Greek terms are more commonly used for metamorphosed rocks, and the Latin for unmetamorphosed:
| Texture | Common | Greek | Latin |
|---|---|---|---|
| Coarse | Gravel(ly) | Psephite (psephitic) | Rudite (rudaceous) |
| Medium | Sand(y) | Psammite (psammitic) | Arenite (arenaceous) |
| Fine | Clay(ey) | Pelite (pelitic) | Lutite (lutaceous) |
[edit] References
- ^ Definition of rudite Accessed on January 1, 2008
- ^ Pettijohn F.J. (1975), Sedimentary Rocks, Harper & Row, ISBN 0-96-045191-2
