Trimerite is a rare beryllium-manganese silicate primarily known from the Långban mines and the Franklin Mining District. It is highly prized by collectors for its distinct, bright yellow-green fluorescence under ultraviolet light. It typically occurs as small, tabular crystals or massive aggregates embedded within metamorphic manganese-bearing rocks.

Hardness

6-7

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Trimerite

Hardness: 6-7
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this trimerite?

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 trimerite with a known reference. Trimerite sits at Mohs 6-7 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Trimerite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Trimerite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, pink, flesh-red, brownish.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, massive, granular.

Often confused with

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

How to tell apart: Streak differs — Trimerite leaves white, Gahnite leaves gray.

Often found alongside trimerite

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

All properties

Chemical formula: CaMn²⁺BeSiO₄
Mohs hardness: 6-7
Density: 3.47 g/cm³
Colors: Colorless Pink Flesh-red Brownish
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Massive, Granular
Cleavage: Poor
Fluorescence: Bright Yellow-green Under SW and LW UV
Rarity: Rare
Uses: Collector
Host rock: Metamorphosed Manganese Ore Deposits
Typical price: $100-500 per specimen

Where rockhounds find trimerite

Classic worldwide localities

Långban, Sweden
Franklin, New Jersey, USA
Sterling Hill, New Jersey, USA

Field-hunting tip

Look in metamorphosed manganese ore deposits country — that is the host setting where trimerite typically forms. If you start seeing willemite, hardystonite, andradite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify trimerite?+

Mohs hardness is 6-7. It typically shows a vitreous luster. The streak is white. Common colors include colorless, pink, flesh-red, brownish.

Where is trimerite found?+

Notable localities include Långban, Sweden; Franklin, New Jersey, USA; Sterling Hill, New Jersey, USA.

How much is trimerite worth?+

Typical asking prices fall in the range of $100-500 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like trimerite?+

Trimerite is most often confused with Willemite, Gahnite, Quartz. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with trimerite?+

Trimerite commonly co-occurs with Willemite, Hardystonite, Andradite, Calcite, Friedelite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does trimerite form in?+

Trimerite typically forms in metamorphosed manganese ore deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is trimerite used for?+

Trimerite is used in collector.

Find trimerite on the map

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