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 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown-red.
- 3Read the lusterHold the specimen under a strong light. Luster: semi-metallic to metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: irregular grains.
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, so Tantalite-(Mg) leaves brown-red, Columbite leaves blackish brown; luster reads semi-metallic to metallic on Tantalite-(Mg) and submetallic on Columbite.
How to tell apart: Streak differs, so Tantalite-(Mg) leaves brown-red, Tantalite-(Fe) leaves black; luster reads semi-metallic to metallic on Tantalite-(Mg) and submetallic to vitreous on Tantalite-(Fe).
How to tell apart: Streak differs, so Tantalite-(Mg) leaves brown-red, Tantalite-(Mn) leaves red, scarlet to black; luster reads semi-metallic to metallic on Tantalite-(Mg) and submetallic to vitreous 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
- 5.5
- Density
- 6.7 g/cm³
- Colors
- Streak
- Brown-red
- Luster
- Semi-metallic to metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Irregular grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- As replacement rims on tantalite-(Mn) crystals in deeply desilicated granite pegmatite that cuts serpentinite near its contact with marble
Where rockhounds find tantalite-(mg)
Classic worldwide localities
- Lipovka pegmatite field, Rezh district, Central Urals, Russia
Field-hunting tip
Where it forms: As replacement rims on tantalite-(Mn) crystals in deeply desilicated granite pegmatite that cuts serpentinite near its contact with marble. If you start seeing tantalite-, columbite-, microlite in float, you are in the right ground. Typical habit: irregular grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify tantalite-(mg)?+
Where is tantalite-(mg) found?+
What rocks look like tantalite-(mg)?+
What minerals are found with tantalite-(mg)?+
What kind of rock does tantalite-(mg) form in?+
What is tantalite-(mg) used for?+
Find tantalite-(mg) on the map
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