Is chrysocolla the same as turquoise
No. Chrysocolla is a copper silicate, hardness about 2 to 4, density 1.93 to 2.4; turquoise is a copper aluminium phosphate at 5 to 6 and 2.86. The 2.63 line.
No. Is chrysocolla turquoise? Chrysocolla is a hydrated copper silicate, hardness about 2 to 4, density 1.93 to 2.4; turquoise is a copper aluminium phosphate, hardness 5 to 6, density 2.86. They are two IMA species that share copper, colour and some mines. A solid piece measuring below 2.63 points to chrysocolla.
In short
- Two species, two chemical classes. Chrysocolla is a silicate and turquoise a phosphate. Chrysocolla's copper runs 33.55% and 37.49% by mass in the two analyses on its Handbook sheet; ideal turquoise is 7.81% copper. Colour is what makes them look alike.
- The 2.63 line. Chrysocolla's recorded density tops out at 2.4 and turquoise's is 2.86. A 20.00 g piece weighs 9.64 to 11.67 g suspended in water as chrysocolla and 13.01 g as turquoise, at least 1.34 g apart. Below 2.63, chrysocolla; above it, go on to the turquoise tests.
- Hardness agrees, by at least one Mohs point. Chrysocolla is about 2 to 4, turquoise 5 to 6. A steel point that bites readily is consistent with chrysocolla; one that barely marks is consistent with turquoise, whose range straddles steel.
- They come out of the same mines. The Globe-Miami district and Morenci in Arizona and Chuquicamata in Chile are named on both Handbook sheets. Turquoise forms in the potassic alteration zone of porphyry copper deposits, chrysocolla in the oxidised portions of many copper deposits.
- Gem silica is neither. Chalcedony coloured by chrysocolla is quartz, hardness 7, as the chrysocolla species page sets out.
| Criterion | Chrysocolla | Turquoise | Does it choose? |
|---|---|---|---|
| Chemical class | Silicate | Phosphate | Yes, but needs a laboratory |
| Formula, Handbook | (Cu,Al)2H2Si2O5(OH)4·nH2O | CuAl6(PO4)4(OH)8·4H2O | - |
| Formula, IMA list (Sept 2026) | (Cu2-xAlx)H2-xSi2O5(OH)4·nH2O | CuAl6(PO4)4(OH)8(H2O)4 | - |
| Copper by mass | 33.55% and 37.49% (two analyses) | 7.81% ideal; 7.19% (Lynch Station analysis) | Only by analysis |
| Hardness (Mohs) | About 2 to 4 | 5 to 6 | Yes: at least 1 point apart |
| Density, measured | 1.93 to 2.4 | 2.86, less if massive | Yes: cut-off 2.63 |
| 20.00 g piece, weight in water | 9.64 to 11.67 g | 13.01 g | Yes on a 0.01 g scale, on solid material |
| Streak | White when pure | White to pale greenish blue | Weakly |
| Lustre | Vitreous, porcelaneous, earthy | Vitreous in crystals; dull to waxy if massive | No |
| Crystal system; largest crystals | Orthorhombic (?); acicular, to 5 mm | Triclinic; to 3 mm | No: both are usually massive |
| Refractive indices | 1.575 to 1.635 | 1.61 to 1.65 | No: they overlap |
Is chrysocolla turquoise? The criteria, in the order that settles it
Chrysocolla is not turquoise: one is a copper silicate and the other a copper aluminium phosphate. The Handbook of Mineralogy gives chrysocolla as (Cu,Al)2H2Si2O5(OH)4·nH2O and turquoise as CuAl6(PO4)4(OH)8·4H2O. The IMA-CNMNC list of minerals lists both as species, chrysocolla with the formula (Cu2-xAlx)H2-xSi2O5(OH)4·nH2O, the two references writing the same variable silicate two ways. The IMA list records the country of first description as unknown for both.
How different is the copper? Worked from the sheets, using Cu 63.546 and O 15.999, so CuO is 79.89% copper: the chrysocolla analysis from Mednorudyansk, Russia, has 42.00% CuO, which is 33.55% copper, and the Kamoya, Congo, analysis has 46.93% CuO, 37.49%. Ideal turquoise has one copper in a formula mass of 813.43, 7.81%. Chrysocolla has more than four times the copper by mass, yet at a glance the two look alike.
The order is density first, hardness second. Density has the wider gap and costs nothing to the specimen. Hardness confirms it, and its technique is on how to test mineral hardness properly. Streak, lustre and refractive index overlap too much to choose, and crystals, the one thing that would settle it by eye, are rarely present: turquoise crystals reach 3 mm and chrysocolla needles 5 mm.
The 2.63 line: a worked density test on a 20 g piece
On a 20.00 g specimen, chrysocolla and turquoise are at least 1.34 g apart in water. Specific gravity is weight in air divided by the weight lost in water. At chrysocolla's density of 1.93 to 2.4 a 20.00 g piece has a volume of 10.36 to 8.33 cm³, so it weighs 9.64 to 11.67 g suspended in water. At turquoise's 2.86 the volume is 6.99 cm³ and the water weight 13.01 g. The midpoint between 2.4 and 2.86 is 2.63, which on this piece is a water weight of 12.40 g.
The decision rule, stated once: below 2.63 is chrysocolla; 2.63 or above, with hardness 5 or more, is turquoise or one of the materials sold as it. The second branch is where how to tell real turquoise from fake takes over, because howlite, magnesite and faustite live on that side of the line and chrysocolla does not. The method, the scale resolution you need and the porous-material caveat are on how to measure specific gravity at home.
Where it fails. The turquoise sheet itself says its density is less if massive, and porous or resin-stabilised material reads low, so a light result on a stabilised cabochon does not prove chrysocolla. The hardness test is the check on that case: stabilised turquoise stays hard, chrysocolla does not.
Why chrysocolla and turquoise turn up on the same labels
Chrysocolla and turquoise come from the same copper districts, which is why old labels confuse them. Reading the Distribution field of both Handbook sheets side by side, three named mines or districts appear on both: the Globe-Miami district, Gila Co., and Morenci, Greenlee Co., Arizona, and Chuquicamata, Chile. Both sheets also name Katanga in the Congo, at different mines. The occurrence fields explain the overlap: turquoise forms in the potassic alteration zone of porphyry copper deposits, and chrysocolla in the oxidised portions of many copper deposits.
Who the answer turquoise is wrong for: anyone holding a blue-green crust that is light in the hand, marks easily and sits on oxidised copper ore with malachite; the chrysocolla sheet lists malachite as an associate and the turquoise sheet does not. Who the answer chrysocolla is wrong for: anyone whose piece resists a steel point and weighs above 2.63; and anyone holding gem silica, which is quartz. Who neither answer suits: an intimate mixture, which is common in the oxidised zone and deserves a label naming both.
More on each species is on the turquoise species page and in the species index; the identification guides are indexed at the collecting guides. Nothing here is offered for sale; the wanted list is the only commercial route.