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, so 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, 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.