Jonesite is an extremely rare barium titanium silicate found almost exclusively in the San Benito River headwaters region of California. It typically appears as small, colorless to pale yellow tabular crystals perched on natrolite, often associated with the iconic blue benitoite and black neptunite.
Is this jonesite?
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 jonesite with a known reference. Jonesite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: bladed, tabular.
Often confused with
Jonesite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside jonesite
Minerals reported to co-occur with jonesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KBa₂Ti₂(Si₅Al)O₁₈·nH₂O
- Mohs hardness
- 3-4
- Density
- 3.25 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Bladed, tabular
- Cleavage
- Distinct on {010}
- Fluorescence
- Dull orange under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In fractures and cavities of brecciated greenstone enclosed in blueschist
Where rockhounds find jonesite
Classic worldwide localities
- Gem mine, San Benito Co., California, USA
Field-hunting tip
Where it forms: In fractures and cavities of brecciated greenstone enclosed in blueschist. If you start seeing neptunite, benitoite, joaquinite in float, you are in the right ground. Typical habit: bladed, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify jonesite?+
Where is jonesite found?+
What rocks look like jonesite?+
What minerals are found with jonesite?+
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Find jonesite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
