Calciosamarskite is a rare niobium-tantalum-rich mineral within the samarskite group characterized by its high calcium content. It typically occurs as black, massive, radioactive grains in complex granite pegmatites and is often identified via X-ray diffraction due to its metamict state.
Is this calciosamarskite?
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 calciosamarskite with a known reference. Calciosamarskite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown to black.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, anhedral grains.
Often confused with
Calciosamarskite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Calciosamarskite leaves brown to black, Samarskite-(Y) leaves dark reddish brown to black, yellow-brown; gray when altered.
How to tell apart: Streak differs, so Calciosamarskite leaves brown to black, Columbite leaves blackish brown; luster reads vitreous on Calciosamarskite and submetallic on Columbite.
Often found alongside calciosamarskite
Minerals reported to co-occur with calciosamarskite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Fe,Fe,Y)(NbTa,Ti)O₄
- Mohs hardness
- 5-6
- Density
- 5.8 g/cm³
- Colors
- Streak
- Brown to black
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, anhedral grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An accessory mineral in RE-rich granite pegmatites, common but not abundant
Where rockhounds find calciosamarskite
Classic worldwide localities
- Mitchell Co., North Carolina, USA
- Woodcox mine, Hybla, Monteagle township, Hastings county, Ontario, Canada
Field-hunting tip
Where it forms: An accessory mineral in RE-rich granite pegmatites, common but not abundant. If you start seeing columbite, zircon, monazite in float, you are in the right ground. Typical habit: massive, anhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify calciosamarskite?+
Where is calciosamarskite found?+
Is calciosamarskite safe to handle?+
What rocks look like calciosamarskite?+
What minerals are found with calciosamarskite?+
What kind of rock does calciosamarskite form in?+
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Find calciosamarskite on the map
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