Geikielite is a rare magnesium titanium oxide mineral that often forms as dark, submetallic tabular crystals. It is most commonly found as water-worn pebbles in gem gravels, particularly in Sri Lanka, or as accessory minerals in contact-metamorphosed limestones.
Is this geikielite?
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 geikielite with a known reference. Geikielite 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: purplish brown.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic.
- 4Match the color rangeCompare against the expected color range: bluish black, brownish black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: granular, prismatic, tabular.
Often confused with
Geikielite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Geikielite leaves purplish brown, Ilmenite leaves black to reddish brown; luster reads submetallic on Geikielite and metallic to submetallic on Ilmenite.
How to tell apart: Streak differs, so Geikielite leaves purplish brown, Hematite leaves cherry-red or reddish brown; luster reads submetallic on Geikielite and metallic or submetallic to dull on Hematite.
How to tell apart: Streak differs, so Geikielite leaves purplish brown, Pyrophanite leaves ocher-yellow, with greenish tinge; luster reads submetallic on Geikielite and metallic to submetallic on Pyrophanite.
Often found alongside geikielite
Minerals reported to co-occur with geikielite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgTiO₃
- Mohs hardness
- 5-6
- Density
- 3.79-4.2 g/cm³
- Streak
- Purplish brown
- Luster
- Submetallic
- Transparency
- Opaque to translucent
- Crystal system
- Trigonal
- Crystal habit
- Granular, prismatic, tabular
- Cleavage
- {1011}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Forms during contact metamorphism of impure magnesian limestones
Where rockhounds find geikielite
Classic worldwide localities
- Crestmore quarry, Riverside Co. and in the Santa Lucia Mountains, Monterey Co., California, USA
- Skeleton Canyon, Cochise Co., Arizona, USA
- Rakwana and Balangoda districts, Sri Lanka
- Baltistan, Kashmir, Pakistan
- Maxwell quarry, near Wakefield, Quebec, Canada
- Fiskenæsset complex, western Greenland
Field-hunting tip
Where it forms: Forms during contact metamorphism of impure magnesian limestones. If you start seeing rutile, spinel, clinohumite in float, you are in the right ground. Typical habit: granular, prismatic, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify geikielite?+
Where is geikielite found?+
What rocks look like geikielite?+
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Find geikielite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
