Martinite is a rare member of the garnet-related group occurring as small, equant crystals. It is primarily found in metasomatized ultramafic rocks known as rodingites. Collectors value it for its rarity and its distinct crystal structure compared to more common silicate minerals.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareGarnet Group family

Martinite

Hardness: 6
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this martinite?

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 martinite with a known reference. Martinite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Martinite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Martinite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white, pale yellow.
5
Look at form & habit
Crystal system: trigonal. Typical habit: equant crystals.

Often confused with

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

Often found alongside martinite

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

All properties

Chemical formula: Ca₅(Si₂O₇)(OH,Cl)₂
Mohs hardness: 6
Density: 2.55 g/cm³
Colors: Colorless White Pale Yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Equant Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Rodingite
Typical price: $50-300 per specimen

Where rockhounds find martinite

Classic worldwide localities

Jas Roux, France
San Benito County, California, USA

Field-hunting tip

Look in rodingite country — that is the host setting where martinite typically forms. If you start seeing calcite, diopside, grossular in float, you are in the right ground. Field specimens usually show a equant crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify martinite?+

Mohs hardness is 6. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white, pale yellow.

Where is martinite found?+

Notable localities include Jas Roux, France; San Benito County, California, USA.

How much is martinite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like martinite?+

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

What minerals are found with martinite?+

Martinite commonly co-occurs with Calcite, Diopside, Grossular. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does martinite form in?+

Martinite typically forms in rodingite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is martinite used for?+

Martinite is used in collector.

Find martinite on the map

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