Presentation on theme: "ROCK AND MINERAL TYPES Minerals are chemical compounds, sometimes specified by crystalline structure as well as by composition, which are found in rocks."— Presentation transcript:
1ROCK AND MINERAL TYPESMinerals are chemical compounds, sometimes specified by crystalline structure as well as by composition, which are found in rocks (or pulverized rocks, known as sand).Rocks consist of one or more Minerals, and fall into three main types depending on their origin and previous processing history:Igneous rocks are ones which have solidified directly from a molten state, such as volcanic lava.Sedimentary rocks are ones which have been re-manufactured from previously existing rocks, usually from the products of chemical weathering or mechanical erosion, without melting.Metamorphic rocks are ones which result from processing, by heat and pressure (but not melting), of previously existing sedimentary or igneous rocks.
5ROCK AND MINERAL TYPESExamples of Igneous Rocks and their constituent minerals include:Basalt, Gabbro, Rhyolite, GraniteFeldspar, Quartz, Amphibole, Pyroxine, OlivineBasalt and Gabbro differ not in composition, but in crystallinity; likewise Rhyolite and Granite.Basalt and Gabbro differ in relative composition, of the five major constituents above, from Rhyolite and Granite.Basalt and Rhyolite have small crystals because they are erupted by volcanoes and cool rapidly from the molten state.Gabbro and Granite have large crystals because they cool slowly from the molten state, underground.
6ROCK AND MINERAL TYPESBasalt/Gabbro and Rhyolite/Granite differ in their proportions of the minerals listed above:Basalt and Gabbro consist mostly of Pyroxine and Olivine. Since these minerals consist largely of magnesium and iron silicates, these rocks are sometimes called mafic.Rhyolite and Granite consist mostly of Feldspar, Quartz, and Amphibole. They are, hence, sometimes called felsic rocks.There is a continuous range in composition between the two extremes, of both composition and crystallinity.
10ROCK AND MINERAL TYPESExamples of Sedimentary Rocks include Limestone, Sandstone, and Shale.Limestone is mostly Calcite (CaCO3) produced by chemical weathering of Feldspar and other silicate minerals. Limestone also is produced from the shells and skeletons of sea life (e.g. plankton and coral).Sandstone and Shale are produced from sand (mostly quartz) and clay minerals (such as kaolinite), which result from mechanical and chemical weathering of igneous rocks.Examples of Metamorphic Rocks include Marble (from Limestone) and Slate (from Shale).