Lópezite is an extremely rare, water-soluble potassium dichromate mineral found almost exclusively in the nitrate deposits of the Atacama Desert. It is highly valued by mineral collectors for its distinct, vibrant orange-red color and glass-like luster, but it must be stored in a dry, airtight environment due to its solubility and susceptibility to environmental humidity.
Is this lópezite?
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 lópezite with a known reference. Lópezite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: orange red, red.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, crusts, or granular.
Often confused with
Lópezite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Lópezite leaves light yellow, Crocoite leaves yellow-orange; luster reads vitreous on Lópezite and adamantine on Crocoite.
How to tell apart: Streak differs, so Lópezite leaves light yellow, Wulfenite leaves white; luster reads vitreous on Lópezite and resinous, subadamantine to adamantine on Wulfenite.
Often found alongside lópezite
Minerals reported to co-occur with lópezite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂Cr₂O₇
- Mohs hardness
- 2.5
- Density
- 2.69 g/cm³
- Colors
- Streak
- Light yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Tabular crystals, crusts, or granular
- Cleavage
- Perfect on {010}; distinct on {100}; distinct on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in vugs in massive nitrate rock
Where rockhounds find lópezite
Classic worldwide localities
- Tarapacá, from Oficina Rosario, Huara, Pampa del Iquique, Chile
- Oficina Maria Elena, near Tocopilla, Pampa del Tocopilla, Chile
- Zapiga, Chile
Field-hunting tip
Where it forms: A rare secondary mineral in vugs in massive nitrate rock. If you start seeing tarapacáite, dietzeite, ulexite in float, you are in the right ground. Typical habit: tabular crystals, crusts, or granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify lópezite?+
Where is lópezite found?+
Is lópezite safe to handle?+
What rocks look like lópezite?+
What minerals are found with lópezite?+
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Find lópezite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
