Is shattuckite turquoise?
Is shattuckite turquoise? No: shattuckite is a copper silicate, 48.43% copper, density 4.11; turquoise a copper aluminium phosphate, 7.81% copper, density 2.86.
No. Shattuckite is a copper silicate, Cu5(SiO3)4(OH)2: orthorhombic, hardness about 3.5, density 4.11, 48.43% copper by mass. Turquoise is a copper aluminium phosphate, CuAl6(PO4)4(OH)8(H2O)4: triclinic, hardness 5 to 6, density 2.86, 7.81% copper. Both are blue copper minerals; weight, hardness and refractive index separate them.
In short
- The verdict. Shattuckite is not a kind of turquoise. The September 2026 IMA-CNMNC Master List lists shattuckite as Cu5(SiO3)4(OH)2, Rd, 1967 s.p., USA, and turquoise as CuAl6(PO4)4(OH)8(H2O)4, A, 1967 s.p., country unknown. One is a silicate, the other a phosphate in the turquoise group.
- The six-to-one copper ledger: what shattuckite is made of. Worked on standard atomic weights, shattuckite is 48.43% copper, 17.12% silicon, 34.14% oxygen and 0.31% hydrogen. Turquoise is 7.81% copper, 19.90% aluminium, 15.23% phosphorus, 55.07% oxygen and 1.98% hydrogen. Copper, oxygen and hydrogen are shared; silicon is only in shattuckite, aluminium and phosphorus only in turquoise. By formula the copper ratio is 6.20 to 1.
- The analyses agree. The shattuckite sheet’s Ajo, Arizona, analysis, CuO 60.41, is 48.26% copper; the turquoise sheet’s Lynch Station, Virginia, analysis, CuO 9.00, is 7.19%: 6.71 to 1. Both sheets’ ideal columns reproduce from the formulas to the hundredth.
- Three separators in hand. Hardness about 3.5 against 5 to 6. Density 4.11 against 2.86, so a 20.00 g piece reads 15.13 g in water as shattuckite and 13.01 g as turquoise, 2.13 g apart. Refractive index: the lowest shattuckite index, 1.753, is 0.103 above the highest turquoise index, 1.65.
- Documented failure: colour and place. Both sheets print blue. Both list the Morenci area of Greenlee Co., Arizona, and Katanga Province, Congo, though at different named mines. They share none of their five named associates, counted by script, but locality does not decide. Shattuckite vs chrysocolla and plancheite vs shattuckite cover shattuckite’s closer look-alikes.
| Property | Shattuckite | Turquoise | Separates? |
|---|---|---|---|
| Formula (IMA); status | Cu5(SiO3)4(OH)2; Rd, 1967 s.p. | CuAl6(PO4)4(OH)8(H2O)4; A, 1967 s.p. | Yes |
| Chemical class | Silicate (pyroxene-type chains, Evans and Mrose 1977) | Phosphate; turquoise group | Yes, by analysis |
| Copper by mass, formula | 48.43% | 7.81% | Yes: 6.20 to 1 |
| Copper by mass, sheet analysis | 48.26% (Ajo, Arizona) | 7.19% (Lynch Station, Virginia) | Yes: 6.71 to 1 |
| Other elements by mass, formula | Si 17.12, O 34.14, H 0.31 | Al 19.90, P 15.23, O 55.07, H 1.98 | Yes: no Si in turquoise, no Al or P in shattuckite |
| Crystal system | Orthorhombic, Pcab | Triclinic, P1̄ | Yes, by X-ray |
| Hardness (Mohs) | About 3.5 | 5–6 | Yes: at least 1.5 steps |
| Density, measured; 20.00 g in water | 4.11; 15.13 g | 2.86, less if massive; 13.01 g | Yes: 2.13 g apart |
| Refractive indices | 1.753, 1.782, 1.815 | 1.61, 1.62, 1.65 | Yes: 0.103 gap |
| Colour; lustre | Deep to medium blue; silky | Sky-blue, bluish green, apple-green, greenish grey; vitreous in crystals, dull to waxy massive | No: blue on both |
| Places on both Distribution fields | Clifton-Morenci district, Greenlee Co.; Katanga Province (Tantara, M’Sesa) | Morenci, Greenlee Co.; Katanga Province (Katonto) | No |
What is shattuckite made of, and how is that different from turquoise?
Copper, silicon, oxygen and hydrogen. The Handbook shattuckite sheet and the IMA list both write Cu5(SiO3)4(OH)2. Worked on standard atomic weights the formula mass is 656.07: copper 48.43%, silicon 17.12%, oxygen 34.14%, hydrogen 0.31%. As oxides that is CuO 60.62, SiO2 36.63 and H2O 2.75, the sheet’s ideal column exactly. Evans and Mrose (1977) describe the structure as brucite-like copper oxide layers with pyroxene-type silicate chains joined to their surfaces.
Turquoise adds aluminium and phosphorus. The IMA list writes CuAl6(PO4)4(OH)8(H2O)4 and the turquoise sheet CuAl6(PO4)4(OH)8·4H2O, the same composition. The formula mass is 813.43: copper 7.81%, aluminium 19.90%, phosphorus 15.23%, oxygen 55.07%, hydrogen 1.98%; as oxides P2O5 34.90, Al2O3 37.60, CuO 9.78 and H2O 17.72, again the sheet’s ideal column. Turquoise has six aluminium atoms to every copper; shattuckite has no aluminium at all.
The six-to-one copper ledger. Per 100 g, shattuckite holds 0.762 moles of copper and turquoise 0.123, which is the 6.20 ratio. The sheets’ own analyses, Ajo shattuckite at CuO 60.41 and Lynch Station turquoise at CuO 9.00, give 48.26% and 7.19% copper, 6.71 to 1. The figures agree with the shattuckite species page (48.43%) and is chrysocolla the same as turquoise (7.81%).
How to tell shattuckite from turquoise
Hardness first. Shattuckite prints about 3.5 and turquoise 5 to 6, at least 1.5 Mohs steps apart; a steel point marks shattuckite readily. The method is on how to test mineral hardness properly.
Weight in water. Shattuckite’s measured density is 4.11 and turquoise’s 2.86, less if massive. A solid 20.00 g piece reads 15.13 g in water as shattuckite and 13.01 g as turquoise, 2.13 g apart; massive turquoise reads lower still. The method is on how to measure specific gravity at home.
Refractive index. Shattuckite α 1.753, β 1.782, γ 1.815; turquoise α 1.61, β 1.62, γ 1.65. The lowest shattuckite index sits 0.103 above the highest turquoise index. Shattuckite’s birefringence is 0.062, turquoise’s 0.04. Three independent numbers point the same way on a solid, single-mineral piece; a mixed crust needs X-ray work.
Why might shattuckite be called turquoise?
Colour. The shattuckite sheet prints deep to medium blue and silky; the turquoise sheet prints sky-blue, bluish green, apple-green and greenish grey, vitreous in crystals and dull to waxy when massive. Blue is on both lines, which is where the confusion starts and where it should end: colour does not choose.
Documented failure: shared districts. By script over the two Distribution fields, the Morenci area of Greenlee Co., Arizona, is on both (the Clifton-Morenci district for shattuckite, Morenci for turquoise), and so is Katanga Province, Congo, at different mines: Tantara and M’Sesa near Kambove for shattuckite, Katonto north of Kolwezi for turquoise. Nevada and New Mexico appear on both as states. Locality narrows nothing to a species.
No shared associates. The shattuckite sheet names chrysocolla, ajoite, malachite, quartz and hematite; the turquoise sheet kaolinite, montmorillonite, allophane, wavellite and pyrite. Counted by script, none is on both lists. Shattuckite’s type locality is the Shattuck mine at Bisbee, per its sheet; the turquoise sheet names none.
What this page does not cover
Imitations and treatments. Dyed and imitation turquoise are covered on how to tell real turquoise from fake and is howlite turquoise, and chrysocolla on is chrysocolla the same as turquoise. This page compares two natural species from their sheets and makes no claim about how any material is sold or labelled.
Copper. Questions about handling copper minerals go to toxic minerals in a collection; this page is not safety advice. More guides are in the collecting guides. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.