Plata Kongsbergita
Plata is a mineral with formula Ag(Hg), in the Nativos group. This specimen comes from Corta San Matilde, Herrerías, Almería, Andalucía, España and joined the Terrium collection in 2003.
Description
Silver foam, or "bird's-nest" silver. Very fragile and light. Tangled dendritic structure with interlaced arborescent branches. Silvery-grey lustre.
History of this specimen
Juan Morillas, who lived about two hundred metres from the extraction area, started going into the mine at 14. He extracted this one at just 19, in 2003, and kept it in his personal collection. He told me he sold these specimens at different prices depending on the buyer: he did not charge foreigners the same as locals. Calculating afterwards, he estimates that over the twenty-five years he was selling material he obtained about €50,000, a figure he would never have imagined at the start. When I bought this one he had very few left. One interesting one at about €70, and three or four more ranging from €150 to €400, but the large ones were not spectacular; they looked like dirty cobwebs with much impurity.
About Plata
Mercurian silver—native silver containing mercury—forms arborescent aggregates and spinel-law twins; it is a rare variety characteristic of the Almería village of Herrerías. Some silver specimens from Corta Santa Matilde analysed in the late 20th century showed a mercury content close to 10%, an unusually high value for this type of mineralisation. Later studies on an old Herrerías "sponge" silver also revealed the presence of mercury, albeit in lower proportion. It is not clear whether this enrichment is characteristic of Santa Matilde—possibly due to deep processes associated with barite—or whether the old Herrerías silvers always carried it without the consequences of their processing (poisonings, illnesses) being recorded. This point remains under discussion among specialists.
About the locality
Historic site in the Cuevas del Almanzora district. Corta Santa Matilde, now buried under millions of tonnes of waste rock, produced in the late 20th and early 21st centuries a good number of specimens of mercurian silver and chlorargyrite (AgCl). These materials soon spread through public and private collections worldwide, making the area a classic reference for these species. Some spots where these silvers were collected had difficult atmospheres, with poorly ventilated gas pockets.
Technical data
- Catalogue No.
- 0284
- Composition
- Ag(Hg)
- Name
- Plata
- Variety
- Kongsbergita
- Group
- Nativos
- Category
- Cupidium
- Mine
- Corta San Matilde
- District / Municipality
- Herrerías
- Province
- Almería
- Region
- Andalucía
- Country
- España
- Size (cm)
- 5 x 3 x 1
- Acquired
- 2003
- Ex-collection
- Juan Morillas López
- Etymology
- From the name of the Kongsberg silver mines, a classic locality for this variety.
- Quality
- Muy buena
- Value trend
- Estable
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