Teruggite is a rare calcium magnesium arsenate borate mineral typically found as small, delicate, colorless to white bladed crystals. It is primarily encountered in boron-rich evaporite deposits where it forms in association with other borate minerals. Due to its scarcity and arsenic content, it is primarily sought after by advanced mineral collectors.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Teruggite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this teruggite?

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 teruggite with a known reference. Teruggite sits at Mohs 2.5, 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: monoclinic. Typical habit: bladed crystals, radial aggregates.

Often confused with

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

mineral

Colemanite

Mohs 4.5

How to tell apart: Colemanite is the harder of the two (Mohs 4.5 vs. 2.5).

Often found alongside teruggite

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

All properties

Chemical formula: Ca₄Mg[AsB₆O₁₁(OH)₆]₂·14H₂O
Mohs hardness: 2.5
Density: 2.149-2.20 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Bladed crystals, radial aggregates
Cleavage: On {001}, good; on {110}, fair
Rarity: Rare
Uses: Collector
Host rock: In lacustrine borate deposits, typically associated with volcanic hot springs and diagensis of playa sediments

Where rockhounds find teruggite

Classic worldwide localities

Loma Blanca borate deposit, eight km southwest of Coranzulí, Jujuy Province, Argentina
Hisarcık borate mine, near Emet, Kütahya Province

Field-hunting tip

Where it forms: In lacustrine borate deposits, typically associated with volcanic hot springs and diagensis of playa sediments. If you start seeing inyoite, calcite, ulexite in float, you are in the right ground. Typical habit: bladed crystals, radial aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify teruggite?+

Mohs hardness is 2.5. Luster: vitreous. The streak is white. Common colors include colorless.

Where is teruggite found?+

Notable localities include Loma Blanca borate deposit, eight km southwest of Coranzulí, Jujuy Province, Argentina; Hisarcık borate mine, near Emet, Kütahya Province.

Is teruggite safe to handle?+

Teruggite contains arsenic and calls for real care. Contains arsenic, which is toxic if ingested, inhaled, or if dust is allowed to settle on skin. Handle with care and wash hands thoroughly after contact.

What rocks look like teruggite?+

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

What minerals are found with teruggite?+

Teruggite commonly co-occurs with Inyoite, Calcite, Ulexite, Aragonite, Realgar, Montmorillonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does teruggite form in?+

Where it forms: In lacustrine borate deposits, typically associated with volcanic hot springs and diagensis of playa sediments. Working float back to the host body is the standard way to chase a fresh occurrence.

What is teruggite used for?+

Teruggite is used in collector.

Find teruggite on the map

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