Calzirtite is a rare zirconium-bearing oxide mineral typically found in carbonatite complexes. It usually occurs as dark, submetallic octahedral crystals or irregular grains, often embedded within carbonate-rich rocks.
Is this calzirtite?
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 calzirtite with a known reference. Calzirtite sits at Mohs 6-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: semimetallic to adamantine, greasy on fractures.
- 4Match the color rangeCompare against the expected color range: dark brown, brown green, light brown, light green, black brown.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: octahedral crystals, granular masses.
Often confused with
Calzirtite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Calzirtite leaves brown, Zircon leaves white; luster reads semimetallic to adamantine, greasy on fractures on Calzirtite and vitreous to adamantine; greasy when metamict on Zircon.
How to tell apart: Streak differs, so Calzirtite leaves brown, Baddeleyite leaves white to brownish white; luster reads semimetallic to adamantine, greasy on fractures on Calzirtite and greasy to vitreous; nearly submetallic in black crystals on Baddeleyite.
How to tell apart: Streak differs, so Calzirtite leaves brown, Perovskite leaves white to grayish white; luster reads semimetallic to adamantine, greasy on fractures on Calzirtite and adamantine to metallic; may be dull on Perovskite.
Often found alongside calzirtite
Minerals reported to co-occur with calzirtite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Zr₅Ti₂O₁₆
- Mohs hardness
- 6-7
- Density
- 4.90-5.01 g/cm³
- Streak
- Brown
- Luster
- Semimetallic to adamantine, greasy on fractures
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Octahedral crystals, granular masses
- Cleavage
- Two partings at ∼80°
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A characteristic accessory mineral in alkalic and ultramafic complexes associated with carbonatites; typically found in residual soils and alluvium
Where rockhounds find calzirtite
Classic worldwide localities
- Ozernyi massif, near Lake Gornoye, Aldan, Sakha, Russia
- Guli ultrabasic pluton, and the Kugda, Magan, and Odikhincha massifs, between the Maimecha and Kotui rivers, far northern Siberia, Russia
- Tazheranskii alkalic massif, west of Lake Baikal, eastern Siberia, Russia
- Seblyavr pluton, Kola Peninsula, Russia
- Found near Chiesa, Val Malenco, Lombardy, Italy
- Kaiserstuhl, Baden-Württemberg, Germany
Field-hunting tip
Where it forms: A characteristic accessory mineral in alkalic and ultramafic complexes associated with carbonatites; typically found in residual soils and alluvium. If you start seeing forsterite, pyroxene, calcite in float, you are in the right ground. Typical habit: octahedral crystals, granular masses. Train your eye for that shape before scanning the outcrop.
Common questions
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Find calzirtite on the map
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