A very fine-grained sedimentary rock made of quartz. Usually made of millions of globular siliceous skeletons of tiny marine plankton called radiolarians. Black chert is called flint. Some mineralogists include chorites in the mica family because the crystals form small flakes. A family of platy silicate minerals that commonly form as a product of rock weathering .
Cobbles are a size of gravel larger than pebbles, but smaller than boulders. .
Along with cementation, this process converts sediments to solid rock. Such a convergence between the Indian and Eurasian plates is responsible for producing the Himalayas. . The rigid, outer layer of relatively low density rock that makes up the continents. A hypothesis proposed by Alfred Wegener suggesting that the continents are not stationary, but have 'drifted' through time. Plate tectonics is the name for the theory that provided the evidence necessary to support Wegener's hypothesis. .