Chalcedony from
Bolivia | |
| Federico Ahlfeld y Jorge Muñoz Reyes (1955) Las Especies Minerales de Bolivia. (Banco Minero de Bolivia) |
| USGS Bulletin #1975 (1992), 257. |
www.mineralmundi.com (in the sulphur deposits) | |
USGS Bulletin # 1975 USGS Bulletin # 1975 |