Terrywallaceite is a rare silver-lead-antimony sulfosalt mineral found in hydrothermal vein deposits. It is primarily identified in lab settings via electron microprobe analysis, appearing as small, opaque metallic grains within associated sulfide assemblages.
Is this terrywallaceite?
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 terrywallaceite with a known reference. Terrywallaceite sits at Mohs ~4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: anhedral grains, massive.
Often confused with
Terrywallaceite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Terrywallaceite is noticeably harder (Mohs ~4 vs. 2-2.5).
How to tell apart: Terrywallaceite is noticeably harder (Mohs ~4 vs. 2-2.5); streak differs, so Terrywallaceite leaves black, Freieslebenite leaves pale steel-gray to silver-white or lead-gray.
How to tell apart: Terrywallaceite is noticeably harder (Mohs ~4 vs. 2.5-3); streak differs, so Terrywallaceite leaves black, Diaphorite leaves steel gray.
Often found alongside terrywallaceite
Minerals reported to co-occur with terrywallaceite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgPb(Sb,Bi)₃S₆
- Mohs hardness
- ~4
- Density
- 6.005 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Anhedral grains, massive
- Cleavage
- Good on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In hydrothermal veins that contain sulfosalt mineralization
Where rockhounds find terrywallaceite
Classic worldwide localities
- Level 390, Vein 14, Mina Herminia, Julcani Mining District, Huancavelica, Peru
Field-hunting tip
Where it forms: In hydrothermal veins that contain sulfosalt mineralization. If you start seeing tetrahedrite, gustavite, barite in float, you are in the right ground. Typical habit: anhedral grains, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify terrywallaceite?+
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Is terrywallaceite safe to handle?+
What rocks look like terrywallaceite?+
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Find terrywallaceite on the map
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