Realgar
Realgar is a mineral with formula As₄S₄, in the Sulfuros group. This specimen comes from Mina Eugenia, La Soterrana, Muñón Cimero, Asturias, España and joined the Terrium collection in 2025.
Description
Red crystals on dark matrix, very fragile.
About Realgar
An intense red arsenic sulphide, very fragile and light-sensitive, prone to alteration. For centuries it was a rare and costly material, known as "the poison of kings". With the Industrial Revolution, arsenopyrite made it common and cheap, and the poison moved from palaces to pantries, to kill rats—and sometimes people. In 1836 a British chemist, James Marsh, saw a murderer acquitted because the arsenic evidence had degraded before trial. Frustrated, he developed an infallible method—the Marsh test—that converted arsenic into a gas and made it reappear as a metallic mirror. Since then, the poison ceased to hide.
About the locality
An Asturian mercury–arsenic occurrence, noted for realgar and orpiment in small veins and alteration zones. Collectable material comes from old dumps. Activity never reached large scale.
Technical data
- Catalogue No.
- 0317
- Composition
- As₄S₄
- Name
- Realgar
- Group
- Sulfuros
- Category
- Meritum Persé
- Matrix
- Caliza carbonosa
- Mine
- Mina Eugenia
- District / Municipality
- La Soterrana
- Province
- Muñón Cimero
- Region
- Asturias
- Country
- España
- Size (cm)
- 7 x 7 x 3
- Weight
- 146 g
- Acquired
- 2025
- Etymology
- From the Arabic «rahj al-ghār», traditionally interpreted as “powder of the mine” or “of the cave”.
- Quality
- Buena
- Value trend
- Estable
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