Topacio
Topacio is a mineral with formula Al₂SiO₄(F,OH)₂, in the Silicatos (Nesosilicatos) group. This specimen comes from San Felipe, Comonfort, Guanajuato, México and joined the Terrium collection in 2025.
Description
Single, thick, well-formed topaz crystal, intense rose-wine colour with orange hues, vitreous lustre and moderate transparency. It rises more than 2 cm above the rhyolitic matrix, is about 1 cm thick, and shows clean, well-defined faces. Free growth in the centre of the cavity gives it a strongly sculptural presence. The volcanic micro-setting is well preserved.
History of this specimen
Daniel Pérez collected it personally during his field campaign (March–September 2025) in the San Felipe rhyolites. For me it is a particularly significant find for the size and thickness of the crystal, preserved intact in its original position despite the fragility of the setting.
About Topacio
Topaz is hard (Mohs 8) yet brittle due to its perfect cleavage. In volcanic cavities it commonly shows free, vertical growth, internal zoning, and well-developed faces. This kind of single crystal is uncommon in rhyolites, where limited space usually restricts development.
About the locality
The vesicular rhyolites of San Felipe (Guanajuato) are silica-rich lavas with cavities formed by gas bubbles. In these vesicles, well-developed topaz crystallises sporadically. Cavities with intact crystals are rare and their recovery requires meticulous work.
Technical data
- Catalogue No.
- 0205
- Composition
- Al₂SiO₄(F,OH)₂
- Name
- Topacio
- Group
- Silicatos (Nesosilicatos)
- Category
- Cavella
- Matrix
- Riolita vesicular
- Mine
- San Felipe
- District / Municipality
- Comonfort
- Province
- Guanajuato
- Country
- México
- Size (cm)
- 3.5 x 3 x 3
- Acquired
- 2025
- Ex-collection
- Daniel Pérez
- Etymology
- From the Greek "topazos", the name of an island in the Red Sea (now Zabargad), although the mineral so named was not topaz.
- Quality
- Muy buena
- Value trend
- Estable