Calomelano
Calomelano is a mineral with formula Hg₂Cl₂, in the Haluros group. This specimen comes from Mina Mariquita, Usagre, Badajoz, Extremadura, España and joined the Terrium collection in 2022.
Description
Siliceous matrix with numerous droplets of native mercury scattered across the surface. A main fracture brings together the three components of the paragenesis: rounded crystals of calomel, well-defined aggregates of eglestonite, and small accumulations of liquid mercury. Under longwave UV, the calomel emits very intense orange fluorescence, reminiscent of incandescent lava. The mercury forms bright, high-surface-tension droplets that speckle the matrix.
History of this specimen
Collected at Mina Mariquita by Carlos González Bargueño himself.
About Calomelano
Native mercury represents the elemental metallic phase. In oxidising environments it can transform into calomel, a secondary chloride that commonly forms microcrystalline aggregates and shows very intense orange fluorescence under longwave UV. Eglestonite is another supergene mercury halide that frequently occurs associated with calomel and native mercury. In this piece, the visible presence of the three phases within a single fracture constitutes a complete paragenesis of considerable interest. Synthetic calomel was used in medicine as a treatment for syphilis before the bacteriological origin of the disease and the high toxicity of the compound were understood.
About the locality
Although Almadén dominates the mercury narrative, Usagre provides a clear example of its surface supergene geochemistry. In the alteration zones, the metal is mobilised, precipitates, and transforms into series of secondary halides, generating associations with calomel, eglestonite and related species.
Technical data
- Catalogue No.
- 0058
- Composition
- Hg₂Cl₂
- Name
- Calomelano
- Group
- Haluros
- Category
- Cavella
- Matrix
- Roca silícea
- Associations
- Eglestonita; Mercurio
- Mine
- Mina Mariquita
- District / Municipality
- Usagre
- Province
- Badajoz
- Region
- Extremadura
- Country
- España
- Size (cm)
- 6.5 x 5 x 3
- Weight
- 88.8 g
- Acquired
- 2022
- Ex-collection
- Carlos González Bargueño
- Etymology
- From the Greek "kalos" (beautiful) and "melas" (black), in reference to its colour. Name used historically before its composition was known.
- Quality
- Notable
- Value trend
- Al alza
Related specimens
- Abellaíta — España
- Abernathyita — España
- Abernathyita — España
- Abernathyita — España
- Aerenita — España
- Aerinita (fibrosa) — España
- Analcima — España
- Analcima — España