Roumaite is a rare member of the perrierite group found primarily in the alkaline rocks of the Langesundsfjord region. It typically appears as small, dark, opaque prismatic crystals and is primarily sought by advanced mineral collectors of rare-earth silicates.

Hardness

5-6

Mohs

Luster

Silky

Streak

White

Transparency

Transparent

mineralrarePerrierite Group family

Roumaite

Hardness: 5-6
Luster: Silky
Streak: White
Transparency: Transparent

No image

Is this roumaite?

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 roumaite with a known reference. Roumaite sits at Mohs 5-6, 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: silky.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals.

Often found alongside roumaite

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

All properties

Chemical formula: (Nb,Ti)(Ca,Na,□)₃(Ca,REE)₄(Si₂O₇)₂(OH)F₃
Mohs hardness: 5-6
Density: 3.33 g/cm³
Colors: Colorless
Streak: White
Luster: Silky
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic crystals
Rarity: Rare
Uses: Collector
Host rock: A late-stage product of hydrothermal activity in cavities in nepheline syenite associated with a peralkaline complex

Where rockhounds find roumaite

Classic worldwide localities

Rouma Island, Los Archipelago, Guinea

Field-hunting tip

Where it forms: A late-stage product of hydrothermal activity in cavities in nepheline syenite associated with a peralkaline complex. If you start seeing aegirine, albite, analcime in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify roumaite?+

Mohs hardness is 5-6. Luster: silky. The streak is white. Common colors include colorless.

Where is roumaite found?+

Notable localities include Rouma Island, Los Archipelago, Guinea.

Is roumaite safe to handle?+

Contains thorium, which is radioactive. Handle with care, store away from other specimens, and wash hands thoroughly after handling.

What minerals are found with roumaite?+

Roumaite commonly co-occurs with Aegirine, Albite, Analcime, Arfvedsonite, Catapleiite, Microcline. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does roumaite form in?+

Where it forms: A late-stage product of hydrothermal activity in cavities in nepheline syenite associated with a peralkaline complex. Working float back to the host body is the standard way to chase a fresh occurrence.

What is roumaite used for?+

Roumaite is used in collector.

Find roumaite on the map

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