Santite is a rare potassium borate mineral typically found as white, granular encrustations within geothermal environments. It is highly soluble in water and unstable in humid air, making it a challenging species for collectors to preserve. It is primarily identified by its association with borate-rich fumaroles in Italy.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Santite

Hardness: 2
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this santite?

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 santite with a known reference. Santite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: granular to compact aggregates.

Often confused with

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

Often found alongside santite

Minerals reported to co-occur with santite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: K[B₅O₆(OH)₄]·2H₂O
Mohs hardness: 2
Density: 1.735 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Granular to compact aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Very rare, formed in fumaroles, probably a product of reaction between potassium-rich solutions and larderellite (Larderello, Italy); as a deposit around a thermal spring (Eagle Borax Spring, California, USA)

Where rockhounds find santite

Classic worldwide localities

Eagle Borax Spring, Furnace Creek district, Death Valley, Inyo Co., California, USA
Larderello, Val di Cecina, Tuscany, Italy

Field-hunting tip

Where it forms: Very rare, formed in fumaroles, probably a product of reaction between potassium-rich solutions and larderellite (Larderello, Italy); as a deposit around a thermal spring (Eagle Borax Spring, California, USA). If you start seeing larderellite, sassolite, aristarainite in float, you are in the right ground. Typical habit: granular to compact aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify santite?+

Mohs hardness is 2. Luster: vitreous. The streak is white. Common colors include colorless.

Where is santite found?+

Notable localities include Eagle Borax Spring, Furnace Creek district, Death Valley, Inyo Co., California, USA; Larderello, Val di Cecina, Tuscany, Italy.

What rocks look like santite?+

Santite is most often confused with Borax, Kernite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with santite?+

Santite commonly co-occurs with Larderellite, Sassolite, Aristarainite, Hydroboracite, Kaliborite, Mcallisterite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does santite form in?+

Where it forms: Very rare, formed in fumaroles, probably a product of reaction between potassium-rich solutions and larderellite (Larderello, Italy); as a deposit around a thermal spring (Eagle Borax Spring, California, USA). Working float back to the host body is the standard way to chase a fresh occurrence.

What is santite used for?+

Santite is used in collector.

Find santite on the map

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