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.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareTourmaline Group family

Foitite

Hardness: 7
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this foitite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch foitite with a known reference. Foitite sits at Mohs 7 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Foitite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Foitite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: dark blue, black, violet-blue.
5
Look at form & habit
Crystal system: trigonal. Typical habit: prismatic crystals.

Often confused with

Foitite vs. its common look-alikes — and how to tell them apart in the field.

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: 3.17-3.21 g/cm³
Colors: Dark Blue Black Violet-blue
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Prismatic Crystals
Cleavage: Indistinct
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $20-150 thumbnail

Where rockhounds find foitite

Classic worldwide localities

San Diego County, California, USA
Island of Elba, Italy
Brumado, Bahia, Brazil
Czech Republic

Field-hunting tip

Look in granite pegmatites country — that is the host setting where foitite typically forms. If you start seeing quartz, albite, muscovite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify foitite?+

Mohs hardness is 7. It typically shows a vitreous luster. The streak is white. Common colors include dark blue, black, violet-blue.

Where is foitite found?+

Notable localities include San Diego County, California, USA; Island of Elba, Italy; Brumado, Bahia, Brazil; Czech Republic.

How much is foitite worth?+

Typical asking prices fall in the range of $20-150 thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like foitite?+

Foitite is most often confused with Schorl, Feruvite, Olenite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with foitite?+

Foitite commonly co-occurs with Quartz, Albite, Muscovite, Garnet. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does foitite form in?+

Foitite typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is foitite used for?+

Foitite is used in collector.

Find foitite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.