Ammonioborite is a very rare ammonium borate mineral typically found as a result of fumarolic activity. It usually occurs as fragile white crusts or small, poorly defined tabular crystals in geothermal areas. Collectors generally acquire it as a micro-mineral from specific historic Italian fumarole sites.
Is this ammonioborite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch ammonioborite with a known reference. Ammonioborite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ammonioborite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ammonioborite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crusts, aggregates of small tabular crystals.
Often confused with
Ammonioborite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ammonioborite
Minerals reported to co-occur with ammonioborite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₃B₁₅O₂₀(OH)₈·4H₂O
- Mohs hardness
- 2
- Density
- 1.74 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Crusts, Aggregates of Small Tabular Crystals
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Fumarolic Environments
- Typical price
- $20-100 per specimen
Where rockhounds find ammonioborite
Classic worldwide localities
- Larderello, Tuscany, Italy
Field-hunting tip
Look in fumarolic environments country, the host setting where ammonioborite typically forms. If you start seeing borax, sassolite, mascagnite in float, you are in the right ground. Field specimens usually show a crusts, aggregates of small tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ammonioborite?+
Where is ammonioborite found?+
How much is ammonioborite worth?+
What rocks look like ammonioborite?+
What minerals are found with ammonioborite?+
What kind of rock does ammonioborite form in?+
What is ammonioborite used for?+
Find ammonioborite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
