Short answer: chrysocolla is a hydrated copper silicate with no fixed formula, colored sky blue to green by copper. On its own it is soft, roughly Mohs 2 to 4, and crumbly. Where silica soaked through it and hardened, the result is chrysocolla chalcedony, sold as "gem silica," which reaches Mohs 7 and costs far more. Most chrysocolla on the market is the softer mixed material, and dyed chalcedony and resin composites imitate it.
Why does chrysocolla's hardness range from 2 to 7?
Ask three references for chrysocolla's hardness and you get three answers, and none of them is wrong. The mineral itself is soft: Minerals.net gives 2 to 4 and webmineral 2.5 to 3.5. The International Gem Society puts the practical problem plainly: a coin could scratch stones with a hardness of 2, while specimens mixed with quartz could reach 7 (IGS). The difference is silica.
| Material | What it is | Mohs | Specific gravity | Typical use |
|---|---|---|---|---|
| Pure chrysocolla | Copper silicate, near amorphous | 2 to 4 | 2.0 to 2.4 | Specimens; crumbles when cut |
| Chrysocolla with quartz or matrix | Chrysocolla intergrown with quartz, iron and manganese oxides | Varies | Varies | Cabochons, palm stones, tumbles |
| Chrysocolla chalcedony ("gem silica") | Chalcedony colored by copper | 7 | 2.55 to 2.91 | Fine jewelry |
| Eilat stone | Mixture of chrysocolla, malachite, turquoise and others | Varies | 2.8 to 3.2 | Cabochons, Israeli jewelry |
The IGS describes fine blue chrysocolla with very little silica as crumbling too easily for cutting or jewelry. At the opposite end, it calls chrysocolla chalcedony the most expensive type of chalcedony, found almost exclusively in Arizona, with copper color in a stone that has the durability of quartz (IGS, Chrysocolla Chalcedony). Everything a buyer sees sits somewhere on that line, and the price follows the silica.
What is chrysocolla, chemically?
Webmineral writes the formula as (Cu,Al)2H2Si2O5(OH)4·n(H2O), with copper at 33.86% of the weight in its calculated composition (webmineral). The "n" is the honest part: water content varies. Minerals.net notes that the formula is not clearly defined, that it carries varying substitution of elements and water, and that most forms are considered amorphous, with a more definite composition only in microcrystals (Minerals.net). It is never in visible crystals. Instead it forms botryoidal crusts, rounded balls, stalactites, veins and fibrous tufts.
The name is older than mineralogy. The IGS traces it to the Greek chrysos, "golden," and kolla, "glue," a name the ancient Greeks applied to a material used in soldering metals, a job borax does today.
Where does chrysocolla form, and which localities matter?
Chrysocolla is a product of weathering. It grows in the oxidized zone of copper deposits, alongside malachite, azurite, quartz, limonite and turquoise, and the oxidation zone guide explains the chemistry that strips copper from sulfide ore and redeposits it near the surface. Minerals.net observes that most chrysocolla comes from copper deposits in arid regions.
- Arizona: the Inspiration Mine (Globe-Miami), the 79 Mine near Hayden, Morenci and Ray, which is known for stalagmites combined with quartz. Arizona is also the near-exclusive source of gem silica.
- Democratic Republic of the Congo: reniform blobs and thick crusts from Kolwezi, and stalactites from the Star of the Congo Mine at Lubumbashi.
- Western Australia: chrysocolla pseudomorphs after azurite from the Whim Creek Copper Mine.
- Peru and Chile: the Lily Mine at Pisco Umay, and deposits in the Atacama Region.
- Israel: the ancient Timna copper mines near Eilat.
The Whim Creek pseudomorphs make a point that applies to the whole family: chrysocolla often replaces other copper minerals, especially azurite, and keeps their shape.
What do Eilat stone, stellarite and parrot wing mean?
Trade names around chrysocolla mostly describe mixtures.
- Eilat stone is a blue to green mix of chrysocolla, malachite, turquoise and other minerals, named after the Israeli city where it was mined. The IGS calls it the national stone of Israel, also sold as "King Solomon Stone." Minerals.net adds a caution: much material sold as Eilat stone does not come from Eilat and is falsely labeled.
- Stellarite is a trade name for a light blue mix of chrysocolla and quartz.
- Parrot wing is chrysocolla mixed with jasper, brownish green in appearance.
- Druzy chrysocolla carries a sparkling skin of tiny quartz crystals, which also protects the soft surface.
Treat any of these as a description, not as a guarantee of origin.
What imitations and treatments should you watch for?
Minerals.net lists chrysocolla as natural and not treated, and that is true of honest material. The market problems are substitution and imitation.
- Dyed chalcedony. The IGS reports simulants made from chalcedony dyed to resemble chrysocolla. Dye collects in fractures and porous bands; a loupe usually shows color concentrated along cracks.
- Composites. Geology.com describes inexpensive "azurite" made from crushed copper minerals in resin, often blended with chrysocolla and malachite (Geology.com). The same binders turn up in bright, cheap chrysocolla beads. The stabilized and reconstituted stones guide shows what binder looks like.
- Sold as turquoise. Because the colors overlap, Minerals.net notes chrysocolla is sometimes used as a cheaper substitute for turquoise and occasionally mislabeled as it.
How do you tell chrysocolla from turquoise, smithsonite and hemimorphite?
Hardness and luster do most of the work. Turquoise and blue chalcedony are harder. Variscite is usually greener without a blue hue. Smithsonite is slightly harder and often lighter in color, and Minerals.net admits it can otherwise be difficult to separate. Blue hemimorphite from China looks similar in botryoidal form but is much denser (SG 3.4 to 3.5) and harder. The full side-by-side is in chrysocolla vs turquoise.
A simple at-home sorting test is weight in the hand against a piece of the same size of known quartz: pure chrysocolla, at SG around 2.0 to 2.2, feels lighter than quartz, while gem silica feels about the same.
How should you care for chrysocolla?
Assume the softest case unless you know the piece is silicified. The IGS recommends a soft brush, mild detergent and warm water, no steam or ultrasonic cleaning, and storage apart from other stones to avoid scratches. Keep raw, crumbly specimens dry. Like any copper mineral, do not lick it, wash your hands after handling raw material, and never sand it dry.
In crystal traditions, chrysocolla is associated with calm communication. That is a cultural meaning, not a measurable property.
Choosing chrysocolla: what to look for
The key question for any chrysocolla is how much silica it contains, because that decides durability and price.
- Luster: a glassy, vitreous polish suggests silicification; a waxy or dull surface means the softer material.
- Color pattern: natural pieces show blue and green with brown and black matrix flecks of iron and manganese oxides. Perfectly even saturated blue at a low price is a warning.
- Weight: composite material is often light; gem silica feels like quartz.
- Labeling: "gem silica" or "chrysocolla chalcedony" should be priced as chalcedony; "chrysocolla" alone usually means the softer mixed stone.
- Shape: palm stones and tumbles suit soft chrysocolla because rounded edges do not chip.
From what we stock:
- Chrysocolla: a 2 inch palm stone and small 1 inch tumbles; rounded forms are the right choice for a soft, variable stone.
- Malachite: includes freeforms with chrysocolla, up to 4.5 x 2.5 x 1.5 inches, showing green malachite bands against chrysocolla blue.
- Azurite on Matrix: the deep blue copper carbonate that chrysocolla often replaces; useful for comparing a carbonate blue with a silicate blue.
- Botryoidal Blue Hemimorphite 0.5 kg: a 7 x 3 x 2 inch display piece of the zinc mineral most often confused with blue chrysocolla.
Digital Towns Market
Chrysocolla and copper minerals in stock
Frequently asked questions
Is chrysocolla the same as turquoise?
No. Chrysocolla is a copper silicate; turquoise is a copper aluminum phosphate and is harder. They form in similar copper deposits and can occur together, as in Eilat stone, which is why chrysocolla is sometimes sold as a cheaper turquoise substitute.
What is gem silica?
Gem silica is the trade name for chrysocolla chalcedony: chalcedony colored blue to blue-green by copper. It has a hardness of 7, is found almost exclusively in Arizona, and is the most expensive type of chalcedony.
Can chrysocolla go in water?
Briefly, for cleaning with mild soap and a soft brush. Do not soak soft or crumbly chrysocolla, avoid steam and ultrasonic cleaners, and dry the piece straight away. Silicified pieces tolerate water better than raw specimens.
Why is my chrysocolla scratched?
Much chrysocolla is softer than many stones it is stored with, and a coin can scratch the softest material. Keep it in its own pouch or box compartment, away from quartz and other harder stones.
Is chrysocolla dyed?
Natural chrysocolla is normally untreated, but dyed chalcedony is sold as chrysocolla. Color pooled in cracks, unnaturally even saturation and a low price for a large, bright piece are the usual signs of dye.
Sources
- Minerals.net, Chrysocolla (mineral): https://www.minerals.net/mineral/chrysocolla.aspx
- Minerals.net, Chrysocolla (gemstone): https://www.minerals.net/gemstone/chrysocolla_gemstone.aspx
- webmineral, Chrysocolla Mineral Data: http://webmineral.com/data/Chrysocolla.shtml
- International Gem Society, Chrysocolla Value, Price, and Jewelry Information: https://www.gemsociety.org/article/chrysocolla-gemstone-information/
- International Gem Society, Chrysocolla Chalcedony Value, Price, and Jewelry Information: https://www.gemsociety.org/article/chrysocolla-chalcedony-gem-information/
- Geology.com, Azurite: https://geology.com/minerals/azurite.shtml