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Spessartine with schorl albite and quartz - Smithsonian Museum of Natural History - 2012-05-17 | by Tim Evanson
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Spessartine with schorl albite and quartz - Smithsonian Museum of Natural History - 2012-05-17

Spessartine (orange) sample on a base of schorl (black crystal), albite (orangish-white), and quartz (barely visible dull brown) on display in the Hall of Geology, Gems, and Minerals of the Smithsonian Museum of Natural History in Washington, D.C.

 

Spessartine is a form of garnet. It is a nesosilicate, which means that the silicon-oxygen tetrahedrons that make up the mineral don't actually bond to one another directly but rather by links. These links are manganese and aluminum.

 

Spessartine was first discovered in Spessart, Germany, in 1832.

 

Albite is a form of feldspar. Feldspar is very common in the Earth's crust. It is formed in igneous rock (right out of the volcano) or in metamorphic rock (sediment that is subject to intense heat and pressure and which takes on a new form). Feldspar is composed of aluminum, silicon, and oxygen crystals that grow in a single direction, but the crystals usually pair up (creating a "groove" effect like an LP record). Usually, a fourth element is present (like sodium, potassium, or calcium), and this determines the actual kind of feldspar you get. Albite contains sodium.

 

Albite is "felsic", which means it is rich in lighter elements (like silicon, oxygen, aluminium, and potassium -- or, in the case of albite, sodium). It is also "plagioclase", which means that it is not only incredibly pure but also can break along two different axes. Albite was first discovered in 1815 in Falun, Sweden. Its name comes from the Latin word "albus" (or white).

 

Schorl is a form of tourmaline. Tourmaline is made of boron, silicon, and oxygen with trace elements of aluminum, iron, magnesium, sodium, lithium, or potassium. It is the most common form of tourmaline and contains little magnesium, sodium, or lithium. Schorl was first discovered in in 1562 in Saxony, Germany. The name is German, but we don't know what it means!

 

Quartz is a mineral made of silica and two sodium molecules. Its easily forms six-sided crystals with six-sided pyramids on the ends.

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Taken on May 17, 2012