Baguette-cut crocoite, 1.65 cts, 6.3 x 5.3 x 2.7 mm, orange-red, Tasmania. Steve Burger, personal collection. © ARK Rare Gems. Used with permission.
Lovely saffron-colored crocoite is quite a rare mineral. Although too soft and brittle for jewelry wear, a few crystals have been faceted for collectors.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
| Data | Value |
|---|---|
| Name | Crocoite |
| Crystallography | Monoclinic. Crystals prismatic, sometimes hollow. |
| Refractive Index | 2.29-2.66 |
| Colors | Red-orange, cherry red, orange, yellowish. |
| Luster | Adamantine to vitreous. |
| Hardness | 2.5 - 3 |
| Fracture | Conchoidal |
| Specific Gravity | 5.9-6.1 |
| Birefringence | 0.370 |
| Cleavage | Indistinct |
| Dispersion | Strong |
| Luminescence | Weak reddish to dark brown (SW); weaker effect in LW. |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Long, UV-Short |
| Transparency | Translucent to transparent. |
| Absorption Spectrum | This mineral shows a distinct absorption band at 5550 but only in thin fragment specimens. It transmits light mainly in the yellow-red region of the spectrum. |
| Formula | PbCrO4 |
| Pleochroism | Trichroic. Orange-red/orange-red/blood red. |
| Optics | a = 2.29-2.31; β = 2.36; γ = 2.66. Biaxial (+), 2V = 57°. |
| Optic Sign | Biaxial + |
| Etymology | From the Greek krokos for “saffron,” in allusion to the color. |
| Occurrence | Secondary mineral in oxidized zones of lead deposits. |
| Phenomena | Chatoyancy |
Crocoite, Red Lead Mine, Dundas, Tasmania, Australia. Photo by Jamain. Licensed under CC By-SA 3.0.
This mineral was previously named crocoise and later crocoisite and is also known as red lead ore.
Tasmania, Australia declared crocoite its official state mineral in 2000.
This rough and cut set features a specimen of lustrous, red-orange crocoite crystals on matrix and a rectangle-cut crocoite gem. 4.5 x 3.3 x 2.1 cm (specimen); 0.58 cts, 4.36 x 3.70 mm (gem); Dundas, Zeehan District, Tasmania, Australia. © Rob Lavinsky, www.iRocks.com. Used with permission.
Crocoite’s intense red-orange to yellow-orange color completely masks its high dispersion.
Crocoite has an orange-yellow streak. Please note: don’t conduct streak testing on finished gems. Test material in inconspicuous spots as a last resort only.
This mineral shows a distinct absorption band at 5550 but only in thin fragment specimens. It transmits light mainly in the yellow-red region of the spectrum.
Crocoite on display at GeoFair 2015. Photo by Kyle Hartshorn. Licensed under CC By 2.0.
Synthetic lead(II) chromate, or “chrome yellow,” has the same chemical formula as crocoite but is only used as a pigment. There’s no known jewelry use for this material.
No known treatments or enhancements.
Dundas, Tasmania produces the world’s best crystals (some gemmy) in large clusters.
The Berezovsk District in Russia, the type locality, produces red crystals.
Other notable sources for gem-quality material include the following:
Crocoites on matrix, 8.6 x 5.7 x 3.5 cm (specimen), Berezovsk Mines, Berezovskii Zavod, Sverdlovsk, Sverdlovskaya Oblast’, Middle Urals, Urals Region, Russia. © Rob Lavinsky, www.iRocks.com. Used with permission.
Gems can weigh up to about 10 carats. However, these are usually not transparent. Tasmania can produce clean, deep red-orange stones up to 1-2 carats.
With a hardness range of 2.5 to 3, crocoites could be cut by coins and knives. Therefore, jewelry use isn’t recommended. For storage suggestions and other information, consult our gemstone collection guide.
Although this mineral contains hexavalent chromium and lead, both toxic, handling crystals or finished gems should pose no problems. However, when cutting this material, avoid ingesting or inhaling particles, wash your hands, and don’t pour solutions with this material down the drain. For more information, consult our articles on toxic and radioactive gem materials and health hazards and safety tips for gem cutters.
Crocoite: Dundas, Tasmania (3.4). Photo © Joel E. Arem, PhD, FGA. Used with permission.
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