Nobleite is a rare calcium borate mineral that typically forms as small, clear, tabular crystals or delicate crusts in arid borate evaporite deposits. Collectors value it for its sharp, glassy crystal habit, though it is usually found in very limited quantities in its type locality in Death Valley.
Is this nobleite?
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 nobleite with a known reference. Nobleite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Nobleite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Nobleite typically shows a subvitreous to pearly luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, radiating aggregates, crusts.
Often confused with
Nobleite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads subvitreous to pearly on Nobleite and earthy on Priceite.
How to tell apart: Luster reads subvitreous to pearly on Nobleite and vitreous to silky on Ulexite.
How to tell apart: Nobleite is noticeably harder (Mohs 3 vs. 2); luster reads subvitreous to pearly on Nobleite and vitreous on Inyoite.
Often found alongside nobleite
Minerals reported to co-occur with nobleite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaB₆O₉(OH)₂·3H₂O
- Mohs hardness
- 3
- Density
- 2.12 g/cm³
- Streak
- White
- Luster
- Subvitreous to Pearly
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Radiating Aggregates, Crusts
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Borate Deposits in Sedimentary Basins
Where rockhounds find nobleite
Classic worldwide localities
- Death Valley, California, USA
- Boron, California, USA
Field-hunting tip
Look in borate deposits in sedimentary basins country, the host setting where nobleite typically forms. If you start seeing colemanite, inyoite, ulexite in float, you are in the right ground. Field specimens usually show a tabular crystals, radiating aggregates, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find nobleite on the map
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