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Tunellite
6 in the gallery
Tunellite is a borate mineral with the chemical formula SrB6O9(OH)2·3H2O. It crystallizes in the monoclinic system and commonly forms tabular to prismatic habits. The mineral exhibits a vitreous to pearly luster and is colorless or white, with a white streak and a relatively soft Mohs hardness of 2.5. Its crystals can be transparent to translucent, and it typically shows perfect cleavage.
- Formula
- SrB6O9(OH)2·3H2O
- Rarity
- Rare
- Stability
- Stable
- Collector interest
- Moderate Interest
- Classification notes
- Borates; Strunz 6.EC.05
Key characteristics
- Crystal system
- monoclinic
- Mohs hardness
- 2.5
- Specific gravity
- 2.4
- Luster
- vitreous, pearly
- Transparency
- transparent, translucent
- Color
- colorless, white
- Streak
- white
- Cleavage
- perfect
- Crystal habit
- tabular, prismatic
Where Tunellite is found
Top localities
- Boron1 specimen
About Tunellite
Notable specimens are associated with localities in the United States, where tunellite has attracted collectors for its delicate, glassy appearance and the subtle interplay of transparency and habit. Specimens from borate-rich environments illustrate the mineral’s tendency to form in layered or tabular forms, which can be visually striking under good lighting.
Collectors value tunellite for its rarity, clear crystallography, and the way its pale coloration contrasts with mineral matrices. While not a dense or highly lustrous specimen, its distinct tabular crystals and monoclinic symmetry provide appealing, diagnostic features that contribute to its study and display in quiet, mineral-focused cabinets.
