Porphyritic Granite

Topics: Granite, Metamorphic rock, Sedimentary rock Pages: 1 (252 words) Published: May 25, 2007
Porphyritic granite
Porphyritic granite is an igneous rock, which consists of orthoclase feldspar, quartz and orthoclase. This type of rock is made up of two different grain sizes, larger crystals referred to as phenocrysts, and smaller granite sized grains. The name for porophyritic originated from the Latin word porphyry which is defined as purple, and is known as a color royalty. This rock has been used as early as 18 AD and was discovered by a Roman legionnaire named Cauius Cominius. It has been used in the construction of items around the world mainly consisting of columns and sculptures or symbols within churches. The reason in which I chose this rock is because its name is very catchy, and I am partial to types of granite. Slate

State is a homogeneous metamorphic rock which is fine grained. Its origin is derived from types of shale sedimentary rock which are composed of clay and volcanic ash. The composition of slate consists mainly of quartz and muscovite or illite, and sometimes includes biotite, chlorite, hematite, and pyrite. Slate is useful towards positions that need to be thin and of various lengths, because of its cleavage. Some common uses for slate are roofing shingles, whetstones, blackboards, and tile. Slate is produced all around the world. Some main regions include the United Kingdom, Italy, Germany, the United States, and China. The reason in which I chose slate is because it has always fascinated me since I was a little kid with its type of cleavage.
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