Terlinguaite is a rare mercury halide mineral that is highly prized by collectors for its brilliant yellow color and strong fluorescence. It is typically found as small, fragile crystals in association with other mercury minerals in specific hydrothermal zones, most notably in the type locality of Terlingua, Texas.
Is this terlinguaite?
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 terlinguaite with a known reference. Terlinguaite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Terlinguaite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Terlinguaite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: yellow, sulfur-yellow, canary-yellow, greenish-yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic to acicular crystals, often as small sprays or encrustations.
Often confused with
Terlinguaite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside terlinguaite
Minerals reported to co-occur with terlinguaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Hg₂ClO
- Mohs hardness
- 2-3
- Density
- 8.7 g/cm³
- Streak
- Yellow
- Luster
- Adamantine
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic to Acicular Crystals, Often as Small Sprays or Encrustations
- Cleavage
- Perfect in One Direction
- Fluorescence
- Bright Yellow Under SW and LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Mercury-bearing Hydrothermal Deposits
- Typical price
- $50-500 thumbnail, $500+ cabinet
Where rockhounds find terlinguaite
1 mapped spotsClassic worldwide localities
- Terlingua District, Texas, USA
- Moctezuma, Sonora, Mexico
- Almaden, Spain
Field-hunting tip
Look in mercury-bearing hydrothermal deposits country — that is the host setting where terlinguaite typically forms. If you start seeing cinnabar, calomel, eglestonite in float, you are in the right ground. Field specimens usually show a prismatic to acicular crystals, often as small sprays or encrustations habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Texas — start trip planning there.
Common questions
How do you identify terlinguaite?+
Where is terlinguaite found?+
Can I find terlinguaite in the United States?+
How much is terlinguaite worth?+
Is terlinguaite safe to handle?+
What rocks look like terlinguaite?+
What minerals are found with terlinguaite?+
What kind of rock does terlinguaite form in?+
What is terlinguaite used for?+
Find terlinguaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
