Sedimentary rocks

Rocks that form from an accumulation of sediments derived from preexisting rocks and/or organic materials. These rocks form by various process that occur on or within the top few kilometers of earth’s crust

Most sedimentary rocks are made up of solid fragments or sediments, often called “clasts”, that have been weathered or eroded from older rocks. Clastic texture rocks are composed of smaller rock fragments called sediments. Classified by their particle size

Pebbles, cobbles and/or boulders some silt sand or clay

Sand Size of particles: from.0006cm to.2cm

Silt particles Particle size: to.006 cm

Clay Clay magnified 1,600 times Particle size: less then.0004 cm

Cementation Often the clasts, such as sand, silt, and pebbles, are cemented together in a process called cementation. This happens as the sediments lose water and the dissolved minerals in the pores of the sediments forming a crystalline mineral material

Chemical sedimentary rock Crystalline Texture When dissolved minerals drop out of water (precipitate), they form a mass of intergrown or interconnected mineral crystals You can see crystals in the rock. The crystals are composed of only one mineral

Bioclastic No crystals, No rock particles. May have shell or shell fragments in it, or be completely black in color consisting of dead organic material Limestone Coal