Chrysocolla: Arizona and New Mexico (Large Specimen ~ 4 inches high). Photo © Joel E. Arem, PhD, FGA. Used with permission.
Pure blue chrysocolla is extremely soft but interesting to gem collectors. On the other hand, chrysocolla that forms as gel mixed with silica and hardens into a blue to blue-green chrysocolla chalcedony is quite hard and a popular jewelry stone.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
| Sillicated | All sizes |
| Solid Color | to /ct |
| Parrot Wing | /ct |
| Data | Value |
|---|---|
| Name | Chrysocolla |
| Crystallography | Monoclinic. Crystals are microscopic, in aggregates; cryptocrystalline, opalline. |
| Refractive Index | 1.575-1.635 |
| Colors | Blue, green, and blue-green in various shades. Mixed with matrix of quartz and oxides of Cu, Fe, and Mn, adding brown and black colors. |
| Luster | Vitreous (if silicified), waxy, dull. |
| Hardness | 2 - 4 (as high as 7 if heavily silicified, or inclusions in quartz). |
| Fracture | Uneven to conchoidal |
| Specific Gravity | 2.00–2.40 |
| Birefringence | 0.023-0.050. |
| Cleavage | None |
| Luminescence | None. |
| Luminescence Present | No |
| Enhancements | Not commonly treated. |
| Transparency | Opaque. |
| Absorption Spectrum | Not diagnostic. |
| Formula | (Cu,Al)2H2Si2O5(OH)4 · Nh2O |
| Optics | a = 1.575-1.585; β= 1.597; γ = 1.598-1.635. Biaxial (-). If material is silicified or is included in quartz, readings may be those of quartz. |
| Optic Sign | Biaxial - |
| Etymology | From the Greek chrysos, “golden,” and kolla, “glue.” This name was applied to a material used by the Ancient Greeks in soldering metals, a function now fulfilled by borax. |
| Occurrence | In the oxidized zone of copper deposits. May be mixed with copper carbonates such as malachite and turquoise. |
“Chrysocolle (chrysocolla),” La Farola Mine, Cerro Pintado, Las Pintadas District, Tierra Amarilla, Copiapó Province, Atacama Region, Chile, by Géry Parent. Licensed under CC By-ND 2.0.
Fine blue chrysocolla with very little silica crumbles too easily for cutting or jewelry use.
Blue to blue-green Eilat stones contain a mix of chrysocolla, malachite, turquoise, and other minerals. Named after the city of Eilat, Israel, where it was mined, this gem is the national stone of Israel and is also called the “King Solomon Stone.” Eilat stones have a specific gravity range of 2.8 to 3.2.
Chrysocollas with druzy quartz crystals on their surfaces make popular jewelry stones.
Other varieties include:
Gemologists have found simulants, such as chalcedonies dyed to resemble chrysocollas.
“Chrysocolla (Stalactite),” Star of the Congo Mine, Lubumbashi, Shaba (Katanga), DRC. © Rob Lavinsky, www.iRocks.com. Used with permission.
Available in large masses of material, weighing several pounds.
Please note the wide range of hardness in this material. A coin could scratch stones with a hardness of 2, while specimens mixed with quartz could have a hardness of 7. If you’re not certain of the composition of your stone, clean and store it with care. Avoid mechanical cleaning such as steam or ultrasonic processes. Instead, use a soft brush, mild detergent, and warm water for cleaning. Store your chrysocollas separately from other stones (as you would treat opals and pearls) to avoid contact scratches. A professional gem lab can ascertain your gem’s physical properties and recommend safe uses. Consult our gemstone jewelry cleaning guide for more recommendations.
Chrysocolla: Arizona (freeform, 13.59). Photo © Joel E. Arem, PhD, FGA. Used with permission.
IGS Newsletter