Foitite is a rare vacancy-dominant member of the tourmaline group, typically forming small, prismatic, dark blue or black crystals. It is most frequently identified through chemical analysis, as it is macroscopically very similar to Schorl and requires specific paragenetic environments to distinguish.
Is this foitite?
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 foitite with a known reference. Foitite sits at Mohs ~7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: bluish black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: prismatic, striated.
Often confused with
Foitite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Foitite leaves grayish white, Schorl leaves white.
How to tell apart: Streak differs, so Foitite leaves grayish white, Feruvite leaves gray.
How to tell apart: Streak differs, so Foitite leaves grayish white, Olenite leaves white.
Often found alongside foitite
Minerals reported to co-occur with foitite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe²⁺₂(Al,Fe³⁺)Al₆Si₆O₁₈(BO₃)₃(OH)₄
- Mohs hardness
- ~7
- Density
- 3.17 g/cm³
- Colors
- Streak
- Grayish white
- Luster
- Vitreous
- Transparency
- Translucent in thin fragments
- Crystal system
- Trigonal
- Crystal habit
- Prismatic, striated
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Probably in granite pegmatites
Where rockhounds find foitite
Classic worldwide localities
- White Queen mine, Pala, San Diego County, California, USA (type locality)
Field-hunting tip
Where it forms: Probably in granite pegmatites. If you start seeing quartz, albite, muscovite in float, you are in the right ground. Typical habit: prismatic, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify foitite?+
Where is foitite found?+
What rocks look like foitite?+
What minerals are found with foitite?+
What kind of rock does foitite form in?+
What is foitite used for?+
Find foitite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
