Haidingerite is a calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 arsenate

Arsenate

The arsenate ion is AsO43−.An arsenate is any compound that contains this ion. Arsenates are salts or esters of arsenic acid.The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As[V]....

 mineral with formula Ca(AsO₃OH)·H₂O. It crystallizes in the orthorhombic crystal system

Crystal system

In crystallography, the terms crystal system, crystal family, and lattice system each refer to one of several classes of space groups, lattices, point groups, or crystals...

 as short prismatic to equant
crystals. It typically occurs as scaly, botryoidal

Botryoidal

A botryoidal texture or mineral habit is one in which the mineral has a globular external form resembling a bunch of grapes as derived from the Greek. This is a common form for many minerals particularly hematite where it is the classically recognized shape. It is also a common form of goethite,...

 or fibrous coatings. It is soft, Mohs hardness of 2 to 2.5, and has a specific gravity

Specific gravity

Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...

 of 2.95. It has refractive indices of nα = 1.590, nβ = 1.602 and nγ = 1.638.

It was originally discovered in 1827 in Jáchymov, Czech Republic

Czech Republic

The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

. It was named to honor Austrian

Austrians

Austrians are a nation and ethnic group, consisting of the population of the Republic of Austria and its historical predecessor states who share a common Austrian culture and Austrian descent....

 mineralogist William Karl von Haidinger (1795-1871). It occurs as a dehydration product of pharmacolite in the Getchell Mine

Getchell Mine

Getchell Mine is an underground gold mine owned by both Barrick Gold, and Newmont Mining, and is located near Winnemucca, Nevada. The operation consists of two underground mines, the Getchell Mine, and Turquoise Ridge. The mining method currently used is drift and fill.The gold deposit is a...

, Nevada

Nevada

Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

.