Tedhadleyite is a rare mercury oxide that forms dark red to black partially hollow, spheroidal masses. It was approved as a distinct mineral species in 2001. It was first described from a prospect pit near the former Clear Creek mercury mine, San Benito County, California, USA.
Is this tedhadleyite?
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 tedhadleyite with a known reference. Tedhadleyite sits at Mohs <3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: red.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine to submetallic.
- 4Match the color rangeCompare against the expected color range: very dark red, black.
- 5Look at form & habitCrystal system: triclinic. Typical habit: anhedral grains, microscopic crystals, spherical.
Often confused with
Tedhadleyite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Tedhadleyite is noticeably harder (Mohs <3 vs. 1.5); streak differs, so Tedhadleyite leaves red, Calomel leaves pale yellowish white.
How to tell apart: Streak differs, so Tedhadleyite leaves red, Terlinguaite leaves lemon-yellow, turning olive-green; luster reads adamantine to submetallic on Tedhadleyite and brilliant adamantine on Terlinguaite.
Often found alongside tedhadleyite
Minerals reported to co-occur with tedhadleyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Hg²⁺Hg¹⁺₁₀O₄I₂(Cl,Br)₂
- Mohs hardness
- <3
- Density
- 9.43 g/cm³
- Colors
- Very dark redBlack
- Streak
- Red
- Luster
- Adamantine to submetallic
- Transparency
- Opaque to translucent
- Crystal system
- Triclinic
- Crystal habit
- Anhedral grains, microscopic crystals, spherical
- Cleavage
- Poor on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- On the wall of a vug in quartz, likely formed, in situ, as a replacement of native mercury, during a period of high activity of I (with lower Cl and Br) in the fluid or vapor phase
Where rockhounds find tedhadleyite
Classic worldwide localities
- Clear Creek claim, San Benito County, California, USA (type locality)
Field-hunting tip
Where it forms: On the wall of a vug in quartz, likely formed, in situ, as a replacement of native mercury, during a period of high activity of I (with lower Cl and Br) in the fluid or vapor phase. If you start seeing native mercury, calomel, cinnabar in float, you are in the right ground. Typical habit: anhedral grains, microscopic crystals, spherical. Train your eye for that shape before scanning the outcrop.
Common questions
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Find tedhadleyite on the map
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