Is orthoclase a mineral or gemstone?

Orthoclase, or orthoclase feldspar (endmember formula KAlSi3O8), is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek for “straight fracture,” because its two cleavage planes are at right angles to each other. It is a type of potassium feldspar, also known as K-feldspar.

Is orthoclase a crystal?

Orthoclase, also known as K-spar and K-feldspar, is a common potassium feldspar mineral that crystallizes in the form of masses, small prismatic shards, elongated crystals, and thin plate-like layers. The largest Orthoclase crystal ever discovered is over 30 feet in length and weighs over 100 tons.

What elements are in orthoclase?

The mineralogical composition of most feldspars can be expressed in terms of the ternary system Orthoclase (KAlSi3O8), Albite (NaAlSi3O8) and Anorthite (CaAl2Si2O8). Chemically, the feldspars are silicates of aluminium, containing sodium, potassium, iron, calcium, or barium or combinations of these elements.

What are the 4 minerals from the feldspar group?

Chemical composition. All the rock-forming feldspars are aluminosilicate minerals with the general formula AT4O8 in which A = potassium, sodium, or calcium (Ca); and T = silicon (Si) and aluminum (Al), with a Si:Al ratio ranging from 3:1 to 1:1.

What is the composition of the mineral orthoclase?

Orthoclase mineral is a silicate of potassium and aluminum, belonging to the Feldspar group. It has the same composition as microcline, but is stable at slightly higher temperatures. It occurs as prismatic, sometimes flat-sided crystals, but in rocks it is usually anhedral.

What is the hardness of an orthoclase gem?

Orthoclase is a mineral with a hardness of 6 out of 10 on the Mohs scale of mineral hardness [?]. These Monoclinicly structured gems are made of potassium aluminum silicate, their full chemical compound being Kalsi3O8.

Why are orthoclase crystals and twins used as gemstones?

Orthoclase crystals and twin s provide information on the formation of minerals and environment al factors. Well shaped crystals and twins are highly sought after by mineral collectors, and the Moonstone variety is used as a gemstone. For additional information, see the gemstone section on Orthoclase and Moonstone.

Where can you find large crystals of orthoclase?

Large crystals of orthoclase are found in igneous rocks known as pegmatite. They are normally no more than a few inches in length, but the largest reported orthoclase crystal was over 30 feet in length and weighed about 100 tons. It was found in a pegmatite in the Ural Mountains of Russia.