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Granite (/ ˈ ɡ r æ n ɪ t / GRAN-it) is a coarse-grained intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous ...
Pegmatitic granite with pink potassium feldspar crystals, surrounding a finer-grained cumulate-filled enclave, Rock Creek Canyon, eastern Sierra Nevada, California. Most pegmatites have a simple composition, often being composed entirely of minerals common in granite, such as feldspar, mica, and quartz. [3]
In 1986, California named benitoite as its state gemstone, a form of the mineral barium titanium silicate that is unique to the Golden State and only found in gem quality in San Benito County. [ 80 ] ^ Colorado is the only state whose geological symbols reflect the national flag's colors: red (rhodochrosite), white (yule marble), and blue ...
It is a favorite collecting area for amateur and serious rock hounds. Scientists from around the world come to Colorado to study the minerals of this region. Because the granite covers a large portion of the Colorado Front Range, there are good mineral collecting areas scattered all over the Pikes Peak region. The collecting localities range ...
Aquamarine can mostly be found in granite pegmatites. [6] It can also be found in veins of metamorphic rocks that became mineralized by hydrothermal activity. [5] Dom Pedro aquamarine in the National Museum of Natural History, Washington, D.C. The largest known example is the Dom Pedro aquamarine found in Pedra Azul, Minas Gerais, Brazil, in ...
Schorl and lithium-rich tourmalines are usually found in granite and granite pegmatite. Magnesium-rich tourmalines, dravites, are generally restricted to schists and marble. Tourmaline is a durable mineral and can be found in minor amounts as grains in sandstone and conglomerate, and is part of the ZTR index for highly weathered sediments. [24]
First found in the United States, unakite has a worldwide distribution, having also been reported in South Africa, Sierra Leone, Brazil, China, India and Australia. Some material labeled unakite lacks the feldspar and is more properly called epidosite , and is also used as beads and cabochons .
This is a list of gemstones, organized by species and types. Minerals There ... Some rocks are used as gems, including: Anthracite; Anyolite; Bauxite; Concretions;