Fersmite is a rare niobium-rich mineral that typically forms as small, elongated prismatic crystals in carbonatites and alkaline pegmatites. Collectors often identify it by its dark color, sub-metallic luster, and its characteristic occurrence alongside calcite and other rare-earth minerals.
Is this fersmite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch fersmite with a known reference. Fersmite sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Fersmite leaves a grayish brown streak.
- 3Read the lusterHold the specimen under a strong light. Fersmite typically shows a resinous to subvitreous to submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, brownish-black, brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals, flattened, often striated.
Often confused with
Fersmite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Columbium Ore is the harder of the two (Mohs 6 vs. 4-4.5); streak differs, so Fersmite leaves grayish brown, Columbium Ore leaves dark red to black; luster reads resinous to subvitreous to submetallic on Fersmite and submetallic on Columbium Ore.
How to tell apart: Euxenite-(Y) is the harder of the two (Mohs 5.5-6.5 vs. 4-4.5); streak differs, so Fersmite leaves grayish brown, Euxenite-(Y) leaves yellowish-brown; luster reads resinous to subvitreous to submetallic on Fersmite and submetallic on Euxenite-(Y).
Often found alongside fersmite
Minerals reported to co-occur with fersmite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Ce,Na)(Nb,Ta,Ti)₂(O,OH,F)₆
- Mohs hardness
- 4-4.5
- Density
- 4.7-4.8 g/cm³
- Colors
- Streak
- Grayish Brown
- Luster
- Resinous to Subvitreous to Submetallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic Crystals, Flattened, Often Striated
- Cleavage
- None; Parting On {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Carbonatites, Alkaline Pegmatites
Where rockhounds find fersmite
Classic worldwide localities
- Vishnevye Mountains, Russia
- Ravalli County, Montana, USA
- Chaffee County, Colorado, USA
- Madagascar
- Norway
Field-hunting tip
Look in carbonatites, alkaline pegmatites country, the host setting where fersmite typically forms. If you start seeing calcite, apatite, phlogopite in float, you are in the right ground. Field specimens usually show a prismatic crystals, flattened, often striated habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fersmite?+
Where is fersmite found?+
Is fersmite safe to handle?+
What rocks look like fersmite?+
What minerals are found with fersmite?+
What kind of rock does fersmite form in?+
What is fersmite used for?+
Find fersmite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
