Siglo Veinte Mine
18.4228° S, 66.5922° W · ± 1 km
Marcasite, Quartz and Siderite from Potosi, Bolivia, with photos of specimens from this locality.
Minerals found here
On the same specimen
A Siglo XX specimen from the Contacto vein carries sharp, water-clear prismatic quartz crystals with small golden marcasite clusters (to about 6 mm) on the same piece, together with a tan siderite coating.
Clear quartz prisms set off by golden sulfide clusters from a classic Bolivian tin-district locality.
Sources: SRC-154
Marcasite at Siglo Veinte Mine
Exceptional marcasite replacement of pyrrhotite in the Llallagua tin-vein system
- Formula
- FeS₂
- Morphology
- Complex groups; pseudomorphs after bladed pyrrhotite
- Typical size
- Groups commonly millimetric to several centimetres
- Color / luster
- Dark golden to gray metallic
- Associated minerals
- Quartzsideritepyrrhotitewavellite
- Surface features
- Preserves fan-shaped pyrrhotite blades in pseudomorphs
- Availability
- Scarce
- History
- Classic material from the Contacto vein and old Siglo Veinte workings
Sources: SRC-018
Quartz at Siglo Veinte Mine
- Formula
- SiO₂
Sources: SRC-154
Siderite at Siglo Veinte Mine
Photo: Robert M. Lavinsky · CC BY-SA 3.0 · Source
- Formula
- FeCO₃
- Morphology
- Sharp hexagonal-looking crystals perched on pyrite
- Associated minerals
- Pyrite
- Availability
- Unknown
- History
- The specimen label gives Llallagua; the dealer notes the habit as unusual for the locality.
Sources: SRC-618
Geology of the locality
- Setting
- Hydrothermal vein mineralization in the Llallagua tin system
- Type
- Hydrothermal
- Host rock
- Quartz-rich vein material
- Region
- Potosi
- Country
- Bolivia
Source of marcasite groups and pseudomorphs after bladed pyrrhotite. Mine position taken from the Mindat locality page (18°25'22"S 66°35'32"W).
Sources
- SRC-018 · Database
Marcasite from Siglo Veinte Mine, LlallaguaMindat.org · Mindat.org - SRC-027 · Database
Siglo Veinte Mine, Llallagua - MindatMindat.org · 2026 · Mindat.org - SRC-154 · Website
Quartz and Marcasite (Siglo XX mine, Llallagua)Mineral Auctions - SRC-618 · Website
File:Siderite-Pyrite-202133.jpgRobert M. Lavinsky · Wikimedia Commons
Draft data from the Provenite workbook. Check entries against the cited sources before relying on them. Photos are open-licence images from Wikimedia Commons; the author and licence are given with each photo.