Acantita Paramórfica tras Argentita
Acantita is a mineral with formula Ag₂S, in the Sulfuros group. This specimen comes from Mina Imiter, Círculo de Tinghir, Tinghir, Drâa-Tafilalet, Marruecos and joined the Terrium collection in 01/09/2025.
Description
Metallic lead-grey cubic crystals on compact white calcite matrix.
History of this specimen
A symbolic piece: it was the wedding gift that Diego Navarro gave Óscar and me in June 2025. It is one of two pieces that a German collector (Christian Rewitzer) had given him many years earlier. It is piece 0016 because that is the number of years we had been together at the time we married.
About Acantita
We know this specimen was originally argentite (Ag₂S) because of its cubic crystallization. But argentite cannot exist at low temperature: below 177 °C, its atoms reorganize. For this reason, the mineralogical standard classifies it as acanthite: it keeps the same chemical formula (Ag₂S), but has a different internal structure. It preserves the original cubic form, but mineralogically it is now acanthite. A mineral does not depend only on its elements, but also on how those elements are arranged in a crystal structure; if the structure changes, the mineral changes, as happens with calcite and aragonite, which share the same formula (CaCO₃) but not the same structure. In short: under normal display-case conditions, a cubic form of Ag₂S should be understood as acanthite paramorphic after argentite.
About the locality
Imiter, in Morocco’s Anti-Atlas, is one of the great names in world silver: it contains around 8,000 tonnes of identified metallic silver. The mine occupies a fault zone several kilometres long in the Jbel Saghro massif and has produced some of the most recognisable acanthites in modern collecting: black, metallic, highly lustrous when fine, occurring as sculptural aggregates in pseudo-octahedral crystals.
Technical data
- Catalogue No.
- 0016
- Composition
- Ag₂S
- Name
- Acantita
- Variety
- Paramórfica tras Argentita
- Group
- Sulfuros
- Category
- Cupidium
- Matrix
- Calcita
- Mine
- Mina Imiter
- District / Municipality
- Círculo de Tinghir
- Province
- Tinghir
- Region
- Drâa-Tafilalet
- Country
- Marruecos
- Size (cm)
- 3 x 2 x 1.5
- Weight
- 6.2 g
- Acquired
- 01/09/2025
- Ex-collection
- Christian Rewitzer > Diego Navarro
- Etymology
- From the Greek "akantha" (thorn), in allusion to the pointed habit common in many specimens; the term "argentite" derives from the Latin "argentum", silver.
- Quality
- Muy buena
- Value trend
- Al alza
Related specimens
- Andradita (Melanita) — Marruecos
- Apatito — Marruecos
- Aragonito — Marruecos
- Arfvedsonita — Marruecos
- Azurita — Marruecos
- Azurita — Marruecos
- Azurita — Marruecos
- Azurita — Marruecos