Idrialite is a rare organic mineral composed of a polycyclic aromatic hydrocarbon found in mercury mines. It is most famous for its distinctive and striking bright blue fluorescence under long-wave ultraviolet light, which makes it highly sought after by mineral collectors.
Is this idrialite?
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 idrialite with a known reference. Idrialite sits at Mohs 1-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Idrialite leaves a yellowish-white streak.
- 3Read the lusterHold the specimen under a strong light. Idrialite typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-white, greenish-yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, granular, or fine-grained aggregates.
Often confused with
Idrialite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Idrialite leaves yellowish-white, Sulfur leaves white.
How to tell apart: Streak differs, so Idrialite leaves yellowish-white, Orpiment leaves yellow.
How to tell apart: Streak differs, so Idrialite leaves yellowish-white, Cinnabar leaves scarlet; luster reads resinous on Idrialite and adamantine on Cinnabar.
Often found alongside idrialite
Minerals reported to co-occur with idrialite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- C₂₂H₁₄
- Mohs hardness
- 1-2
- Density
- 1.4 g/cm³
- Streak
- Yellowish-white
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, Granular, Or Fine-grained Aggregates
- Cleavage
- None
- Fluorescence
- Bright Blue Under UV Light
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Mercury-bearing Hydrothermal Deposits and Bituminous Shales
- Typical price
- $50-300 per specimen
Where rockhounds find idrialite
Classic worldwide localities
- Idrija, Slovenia
- Terlingua, Texas, USA
Field-hunting tip
Look in mercury-bearing hydrothermal deposits and bituminous shales country, the host setting where idrialite typically forms. If you start seeing cinnabar, mercury, pyrite in float, you are in the right ground. Field specimens usually show a massive, granular, or fine-grained aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find idrialite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
