Tantalite-(Mg) is a rare magnesium-dominant member of the columbite group, occurring primarily in complex granitic pegmatites. It is typically found as dark, submetallic tabular crystals that can be difficult to distinguish from iron or manganese-dominant analogues without chemical analysis.
Is this tantalite-(mg)?
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 tantalite-(mg) with a known reference. Tantalite-(Mg) sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Tantalite-(Mg) leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Tantalite-(Mg) typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: brown, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular to prismatic crystals, often as striated aggregates.
Often confused with
Tantalite-(Mg) vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Tantalite-(Mg) leaves black, Columbium Ore leaves dark red to black.
How to tell apart: Streak differs — Tantalite-(Mg) leaves black, Tantalite-(Mn) leaves reddish-brown to black; luster reads submetallic on Tantalite-(Mg) and submetallic to resinous on Tantalite-(Mn).
Often found alongside tantalite-(mg)
Minerals reported to co-occur with tantalite-(mg). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgTa₂O₆
- Mohs hardness
- 6
- Density
- 6.0-6.6 g/cm³
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular to Prismatic Crystals, Often as Striated Aggregates
- Cleavage
- Distinct On {100}
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Granitic Pegmatites
- Typical price
- $50-500 depending on specimen size and clarity
Where rockhounds find tantalite-(mg)
Classic worldwide localities
- Alto Ligonha, Mozambique
- Congo
- Western Australia
Field-hunting tip
Look in granitic pegmatites country — that is the host setting where tantalite-(mg) typically forms. If you start seeing beryl, spodumene, albite in float, you are in the right ground. Field specimens usually show a tabular to prismatic crystals, often as striated aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify tantalite-(mg)?+
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How much is tantalite-(mg) worth?+
What rocks look like tantalite-(mg)?+
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Find tantalite-(mg) on the map
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