Usually forms from molten rock rich in water or other volatiles that facilitate the growth of large crystals. Forms sills and dikes . Mudstone, shale, siltstone, and claystone are all pelitic . A stream that runs continuously throughout the year. The ability of a rock or other material to allow water to flow through its interconnected spaces.
Permeable bedrock makes a good aquifer, a rock layer that yields water to wells.
See porosity . The study of rocks. May be a petrologist, a stone mason, a rock climber. An igneous rock texture in which the mineral grains are large enough to be seen with the unaided eye and are of approximately equal size. The eon beginning about 570 million years ago and continuing to the present.