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Chemical Formula | PbCrO4 | ||||||
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Composition | Lead chromate | ||||||
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Color | Bright orange-red | ||||||
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Streak | Orange-red with a yellow tint | ||||||
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Hardness | 2½ - 3 | ||||||
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Crystal Forms and Aggregates |
(Monoclinic) Occurs as elongated prismatic crystals, which are striated vertically. Crystals are rarely large and single. Most commonly as reticulated aggregates, acicular groupings, elongated needles, grainy, encrusting, and as disorganized groupings of small prismatic crystals. Crystals are sometimes partially hollow. | ||||||
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Transparency | Translucent | ||||||
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Specific Gravity | 5.9 - 6.1 | ||||||
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Luster | Adamantine | ||||||
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Cleavage | 3,1 - prismatic | ||||||
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Fracture | Conchoidal to uneven | ||||||
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Tenacity | Brittle, but very slightly sectile | ||||||
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Other Names |  Red Lead Ore |
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In Group | Sulfates ; Chromates | ||||||
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All About | Because of its beauty, Crocoite is a mineral
that fascinates collectors. It was first found in Russia
and later in other European localities, but only
sparingly, and seldom in attractive examples. Then the
Australian occurrence on the island of Tasmania was
discovered, where large, brilliant, well-formed crystals
were obtained. These specimens were exhaustively
collected, and, almost immediately, these large and
brilliant specimens were gone. Only few were fortunate to
get such specimens. Now, only fragile aggregates of small
crystals can be there, and, although attractive, are
insignificant when compared to the original crystals.
Except for those large and tough crystals, all other
specimens are fragile and care must be taken when
handling them. ((A rumor exists that Crocoite specimens dull in luster with exposure to air, but I have yet to see this.)) |
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Uses | Crocoite was at one time a main ore of chromium, but it is now too rare to be used. Crystals are highly sought after by mineral collectors because of its attractive color. | ||||||
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Striking Features | Color and luster, crystal habits, and localities | ||||||
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Complex Tests | Soluble in hydrochloric acid | ||||||
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Popularity (1-4) | 2 | ||||||
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Prevalence (1-3) | 3 | ||||||
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Demand (1-3) | 1 | ||||||
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Distinguishing Similar Minerals |
Wulfenite, Cinnabar, and Vanadinite - form in different crystals Realgar - softer, lighter in weight Cuprite var. Chalcocitrite - Harder, occurs in different localities |
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Commonly Occurs With |
Wulfenite, Cerussite, Vanadinite, Pyromorphite, Galena | ||||||
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Noteworthy Localities |
Dundas, on the island of Tasmania,
Australia, is where Crocoite is most abundant, and where
the most magnificent crystals were obtained. All other
localities listed yielded only minor amounts. It was
found in Sverdlovsk, Ural Mountains, Russia; Callenberg,
Saxony, Germany; Nontron, France; Labo, Philippines; and
Congonhas de Campo, Brazil. In the U.S., only small amounts were found, only capable of being micromounts. Occurrences include the Mammoth Mine, Tiger, Pinal Co., Arizona; the El Dorado Mine, Indio, Riverside Co., California; and Darwin, Inyo Co., California. |
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Picture Icon Links |
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Picture Links | 1. Grouping
of small crystals 2. Striated crystal 3. Intergrown crystals |
