Derbylite is an uncommon complex oxide mineral usually occurring as tiny, dark, prismatic crystals or needle-like radial aggregates. It is primarily found in iron-rich metamorphic environments where it is often associated with other rare antimony-bearing minerals.
Is this derbylite?
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 derbylite with a known reference. Derbylite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish black.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous to metallic.
- 4Match the color rangeCompare against the expected color range: black, pitch black, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: granular, prismatic.
Often confused with
Derbylite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Derbylite leaves brownish black, Ilmenite leaves black to reddish brown; luster reads resinous to metallic on Derbylite and metallic to submetallic on Ilmenite.
How to tell apart: Streak differs, so Derbylite leaves brownish black, Hematite leaves cherry-red or reddish brown; luster reads resinous to metallic on Derbylite and metallic or submetallic to dull on Hematite.
Often found alongside derbylite
Minerals reported to co-occur with derbylite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺₄Ti₃Sb³⁺O₁₃(OH)
- Mohs hardness
- 5
- Density
- 4.53-4.62 g/cm³
- Colors
- Streak
- Brownish black
- Luster
- Resinous to metallic
- Transparency
- Opaque, translucent in small grains
- Crystal system
- Monoclinic
- Crystal habit
- Granular, prismatic
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In cinnabar-bearing placer gravels (Tripuhy, Brazil); in microcrystalline barite and in cavities within metasomatically mineralized dolostones (Buca della Vena mine, Italy)
Where rockhounds find derbylite
Classic worldwide localities
- Tripuhy, near Ouro Preto, Minas Gerais, Brazil
- Buca della Vena iron mine, north of Stazzema, Apuan Alps, Tuscany, Italy
Field-hunting tip
Where it forms: In cinnabar-bearing placer gravels (Tripuhy, Brazil); in microcrystalline barite and in cavities within metasomatically mineralized dolostones (Buca della Vena mine, Italy). If you start seeing roméite, tripuhyite, monazite in float, you are in the right ground. Typical habit: granular, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify derbylite?+
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Is derbylite safe to handle?+
What rocks look like derbylite?+
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Find derbylite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
