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.
|Crystallography||Monoclinic. Crystals prismatic, sometimes hollow.|
|Colors||Red-orange, cherry red, orange, yellowish.|
|Luster||Adamantine to vitreous.|
|Hardness||2.5 - 3|
|Specific Gravity||5.9 - 6.1|
|Luminescence||Weak reddish to dark brown (SW); weaker effect in LW.|
|Transparency||Translucent to transparent.|
|Absorption Spectrum||See "Identifying Characteristics" below.|
|Pleochroism||Trichroic. Orange-red to blood red.|
|Optics||a = 2.29-2.31; β = 2.36; γ = 2.66. Biaxial (+), 2V = 57°.|
|Etymology||From the Greek krokos for “saffron,” in allusion to the color.|
|Occurrence||Secondary mineral in oxidized zones of lead deposits.|
Crocoite’s intense red-orange to yellow-orange color completely masks its high dispersion.
This mineral was previously named crocoise and later crocoisite and is also known as red lead ore. Synthetic lead(II) chromate, or “chrome yellow,” has the same chemical formula as crocoite but is only used as a pigment.
Tasmania, Australia declared crocoite its official state mineral in 2000.
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.
Dundas, Tasmania produces the world’s best crystals (some gemmy) in large clusters.
The Beresov District in Russia, the type locality, produces red crystals.
Other notable sources for gem-quality material include:
- United States: Tiger, Arizona (very tiny crystals); California.
- Brazil: Minas Gerais.
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.
- Devonian Group (Calgary, Alberta, Canada): 14.5 (orange, Tasmania).
- Smithsonian Institution (Washington, D.C): 5.7 (orange-red, Tasmania).
With a hardness range of 2.5 to 3, crocoites could be cut by coins and knives. Therefore, jewelry use is not recommended. For storage suggestions and other information, consult our gemstone collection guide.
Please note, this mineral contains both hexavalent chromium and lead, which are toxic. When working with this material, avoid ingesting or inhaling particles, wash your hands, and don’t pour solutions with this material down the drain.