Crocoite
Lead chromate (PbCrO4)
A striking lead chromate mineral prized for its brilliant orange-red prismatic crystals, with the finest specimens from Tasmania.
- Mohs hardness
- 2.5-3
- Color
- Bright orange-red to red
- Type
- mineral
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Overview
Crocoite is lead chromate (PbCrO4), a secondary mineral instantly recognizable by its vivid orange-red to red color. It crystallizes in the monoclinic system, typically forming slender, elongated prismatic crystals with a brilliant adamantine luster.
Discovered in the Ural Mountains of Russia in the 18th century, crocoite holds historical importance: it was the mineral in which the element chromium was first discovered. Its name derives from the Greek word for saffron.
The world's most spectacular crocoite specimens come from the Dundas region of Tasmania, where dazzling clusters of bright red crystals are highly prized by collectors.
Formation & geology
Crocoite is a secondary mineral that forms in the oxidized zones of lead ore deposits where chromium-bearing rocks are also present. Weathering of primary lead minerals such as galena releases lead, which combines with chromate ions derived from nearby chromium-rich host rocks.
This combination of conditions is geologically uncommon, which makes crocoite a relatively rare mineral overall, though locally abundant at favorable sites.
The famous Tasmanian deposits at Dundas, Adelaide, and Red Lead mines formed where oxidizing lead veins intersected ultramafic rocks supplying the necessary chromium. Russia's Berezovskoe deposit was the original discovery locality.
How to identify it
Crocoite is identified by its intense orange-red to red color, brilliant adamantine to vitreous luster, and habit of forming long, slender prismatic crystals, often in radiating or hollow clusters. Its streak is orange-yellow.
It is soft (Mohs 2.5 to 3) and relatively heavy due to its high lead content. These properties, combined with its distinctive crystal form, make it hard to confuse with other minerals.
Look-alikes include wulfenite (more tabular, yellow to orange) and vanadinite (hexagonal crystals, deeper red); crocoite's slender prisms and unique color help separate it.
Uses & significance
Crocoite has no significant industrial use today, but it is of major historical importance as the mineral from which chromium was first isolated in 1797. The pigment chrome yellow was historically derived from synthetic lead chromate.
Its primary value now is as a collector's specimen. Fine Tasmanian crocoite clusters are among the most sought-after and visually stunning mineral specimens in the world, commanding high prices.
Because it contains lead and chromium, crocoite should be handled carefully and not ingested or inhaled as dust.
Frequently asked questions
Why is crocoite historically important?
Chromium was first discovered in crocoite in 1797 by Louis Vauquelin, and the element was named for the colorful chromium compounds the mineral contains.
Where are the best crocoite specimens found?
The Dundas mineral field in Tasmania, Australia, produces the world's finest crocoite, with brilliant red prismatic crystal clusters.
Is crocoite toxic?
It contains both lead and chromium, so specimens should be handled with care, kept out of reach of children, and never powdered or ingested.
Can crocoite be cut as a gemstone?
It is too soft and fragile (Mohs 2.5 to 3) for practical jewelry, so it is valued almost entirely as a mineral specimen.
Crocoite guides
In-depth guides for identifying, valuing, and understanding Crocoite.
Crocoite identified by the community
Real specimens identified with Rock Identifier.
