Danburite
Danburite is calcium borosilicate, CaB2Si2O8, crystallizing in the orthorhombic system as prismatic crystals that closely resemble topaz at a glance. It was first identified near Danbury, Connecticut, which gave the mineral its name, though the finest modern specimens come from Mexico and Madagascar. Its glassy luster and typically pale coloring make it a favorite among faceted-gem collectors seeking an affordable topaz alternative.
Danburite properties at a glance
| Type | Minerals |
|---|---|
| Chemical formula | CaB2Si2O8 |
| Mohs hardness | 7–7.5 |
| Crystal system | Orthorhombic |
| Luster | Vitreous |
| Streak | White |
| Cleavage | Poor, indistinct basal |
| Fracture | Conchoidal |
| Specific gravity | 2.97–3.02 |
| Transparency | Transparent to translucent |
| Common colors | Colorless, Pale yellow, Brownish yellow, Pink |
| Rarity | common |
Geology & background
Danburite forms in contact metamorphic zones around granitic intrusions and in certain hydrothermal or skarn environments, where boron-bearing fluids react with calcium-rich host rock to produce this relatively uncommon borosilicate. The original Connecticut locality yielded only modest material, but subsequent discoveries in Charcas, Mexico, and in Madagascar and Myanmar have produced larger, gemmy crystals that now dominate the specimen and gem trade. Because danburite shares topaz's general appearance, colorless to pale yellow or pink coloring, and comparable hardness, the two are sometimes confused in mixed mineral lots, though their crystal habits and cleavage differ once examined closely.
Collectors interested in boron minerals often pair danburite with other borosilicates like axinite to illustrate how boron substitutes into otherwise silicate-dominated mineral structures.
How to identify Danburite
Danburite crystals are typically prismatic with a wedge-shaped termination, showing a vitreous luster, a white streak, and colors that range from colorless to pale yellow, brown, or pink. Hardness of 7 to 7.5 is close to topaz, but danburite lacks topaz's perfect basal cleavage, breaking instead with an uneven to subconchoidal fracture, which is the most reliable way to separate the two in hand specimen. Its orthorhombic prisms often show fine vertical striations along their length, another useful clue when distinguishing it from quartz or topaz.
- Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
- Use multiple photos when possible, including a fresh surface and a close view of texture.
Where Danburite is found
Reported from multiple localities worldwide; verify locality against specimen provenance when available.
How much is Danburite worth?
| Entry-level specimen | $2 |
|---|---|
| Typical collector specimen | $20 |
| Premium specimen | $150+ |
Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.
Common uses
- Collector specimens
- Education
- Field identification
- Industrial or lapidary use when suitable
Interesting facts
- Danburite is named for Danbury, Connecticut, the town where it was first identified in the early nineteenth century.
- It closely resembles topaz in appearance but lacks that mineral's perfect cleavage, breaking unevenly instead.
- Some danburite crystals fluoresce a pale blue or sky-blue color under shortwave ultraviolet light.
Care & safety
Handle as a collector specimen until hardness, cleavage, and fracture are verified.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.
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