Realgar
Realgar is a mineral with formula As₄S₄, in the Sulfuros group. This specimen comes from Getchell Mine, Adam Peak, Humboldt County, Nevada, Estados Unidos and joined the Terrium collection in 1973.
Description
Scarlet-red prismatic crystals, transparent, with adamantine lustre. Densely developed on grey matrix with dark limonitic zones. Some crystals show pointed terminations and are partly set in cavities, accompanied by thin yellowish alteration crusts.
About Realgar
An intense red arsenic sulphide, highly sensitive to light and the environment, tending to alter progressively to pararealgar. One of the most fragile and visually striking minerals in hydrothermal parageneses, valued for its lustre but very delicate in conservation. Arsenic bound in realgar has had a notable historical role as poison and pigment: in the 19th century, with the onset of the chemical era, arsenical compounds were widely used in intense green dyes and wallpapers, leading to numerous deaths associated with their high toxicity. Pararealgar, its yellow–orange polymorph, results from this alteration: it appears inevitably when the piece is exposed to sunlight, degrades the structure of the original crystal, and ends as yellow powder in its final stage.
About the locality
Getchell Mine, in Humboldt County, is a classic United States locality for realgar of exceptional colour and lustre, associated with stibnite, orpiment and quartz. It forms part of the Potosi gold district, worked since 1937.
Technical data
- Catalogue No.
- 0255
- Composition
- As₄S₄
- Name
- Realgar
- Group
- Sulfuros
- Category
- Meritum Persé
- Matrix
- Cuarzo
- Mine
- Getchell Mine
- District / Municipality
- Adam Peak
- Province
- Humboldt County
- Region
- Nevada
- Country
- Estados Unidos
- Size (cm)
- 3.3 x 3.5 x 2.2
- Weight
- 17 g
- Acquired
- 1973
- Ex-collection
- W. Leicht (1973) > Dr. G. Jung
- Etymology
- From the Arabic "rahj al-ghar" ("powder of the mine").
- Quality
- Muy buena
- Value trend
- Al alza
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