Silver with Acanthite after Argentite, Chañarcillo Mining District, Copiapó Province, Atacama, Chile
A rare opportunity for the serious silver mineral collector, this self-standing specimen is accompanied by an old typewritten label reading “Native Silver & Argentite* XLS, Chanarcille, Atacama, Chile.” The famous Chañarcillo silver mining district produced $100,000,000 of silver between 1830 and 1880. This long-closed locality is very well known for Proustite crystals and has produced many good acanthite specimens, but today they are rarely offered for sale.
This specimen presents interesting and unusual pseudomorphs of Acanthite after Argentite. The dendritic material shown in the macro photography may be Acanthite ps after Silver (compare to Mindat GH4-APD). There is minor microcrystalline proustite visible in the matrix. A lovely, bright ruby red grain of Proustite is also observable under magnification. These specimens likely came out many, many decades ago. A very few have been recirculated from old private and government/national museum collections. There are only 14 photographs in the Mindat photo gallery. As such, this is likely an unusual specimen from an uncommon locality. The matrix is composed of quartz and calcite. The latter fluoresces deep red. Sourced from a forty-year-old collection.
Dimensions: 65 x 45 x 25 mm. Weight: 180 g (6.3 oz).
* The name 'argentite' refers to the high-temperature form of silver sulphide, only stable over 177°C. Below this temperature, any samples of 'argentite' convert to acanthite. The name argentite is therefore used (confusingly) by some to describe pseudo-cubic pseudomorphs of silver sulphide (acanthite) where the original crystal form of the high-temperature cubic argentite has remained.
