Realgar, Lengenbach Quarry, Switzerland
Mineral Matters #617
The Mineral of the Week Facebook Group got off to a bit of a slow start this year. But it is now up and going again. The current theme is arsenic-bearing minerals.
One of the arsenic sulphide minerals is the very colourful realgar, formula As4S4. It is known for its vibrant red to orange-red colour, which makes it visually striking. It often forms prismatic or tabular crystals.
Realgar can fade over time due to exposure to light, turning into a yellowish or greyish hue. This is due to the transformation of realgar into other arsenic minerals, such as pararealgar or orpiment.
It is typically found in hydrothermal veins and hot spring deposits and often occurs alongside other arsenic minerals, such as orpiment (As2S3), and may be associated with other sulphide minerals.
Historically, realgar has been used as a pigment due to its vivid colour. It was also used in traditional medicine, now discouraged due to the toxicity of arsenic. Handling realgar can be hazardous, and inhaling its dust or ingesting it can lead to arsenic poisoning.
The Lengenbach Quarry is a renowned mineral locality situated in the Binn Valley of Valais, Switzerland. It is particularly famous for its unique and diverse mineralogy, making it a significant site for mineral collectors and researchers.
Below: 2344 Realgar, Lengenbach Quarry, Fäld (Imfeld; Im Feld; Feld), Binn Valley, Wallis (Valais), Switzerland. Width of view 3mm.
