Variscite vs turquoise
Variscite is not a type of turquoise: an aluminium phosphate with no copper and one Al per phosphorus, against 1.5 and 7.81% copper. Hardness 4.5 vs 5 to 6.
No: variscite is not a type of turquoise. Variscite is Al(PO4)(H2O)2, an orthorhombic aluminium phosphate with no copper and one aluminium per phosphorus; turquoise is triclinic CuAl6(PO4)4(OH)8(H2O)4, 7.81% copper, with 1.5 aluminium per phosphorus. On the sheets variscite is softer, hardness 4.5 against 5 to 6, and lighter, 2.57 to 2.61 against 2.86.
In short
- Criteria first. In order of strength: an analysis (copper, and aluminium per phosphorus), then a refractometer (the 1.6 gap on variscite, not repeated here), then the optic sign, biaxial (−) against (+), then hardness, 4.5 against 5 to 6, then weight. Colour comes last: the International Gem Society variscite article says blue-green variscite with black spiderweb patterns may resemble turquoise.
- The 1-or-1.5 rule. Variscite’s IMA formula has 1 aluminium per phosphorus; turquoise’s has 6 to 4, 1.5. Worked from the Handbook of Mineralogy sheets’ own analyses on standard atomic weights, the Lucin, Utah, variscite gives 1.008 and the Lynch Station, Virginia, turquoise 1.489, with 0.94 copper per four phosphorus (the sheet prints Cu0.95). An analysis that finds aluminium and phosphorus near one to one and no copper is the variscite side.
- Documented failure: no copper does not mean no turquoise group. A script over the September 2026 IMA-CNMNC Master List finds 5 rows with turquoise’s formula shape: turquoise and chalcosiderite carry copper; faustite (zinc), aheylite (ferrous iron) and planerite carry none. All five have six trivalent cations to four phosphorus. Copper names turquoise the species; the 1.5 ratio is what the group shares, and variscite does not.
- The balance helps, with a caveat. A 20.00 g piece reads 12.22 to 12.34 g in water as variscite and 13.01 g as turquoise at the sheet’s 2.86, 0.67 to 0.79 g apart. The turquoise sheet itself adds less if massive, so porous material can close the gap; why that matters is set out on the variscite page. Method on how to measure specific gravity at home.
- Who each name is wrong for. “Turquoise” is wrong for a copper-free green nodule whose analysis runs near one aluminium per phosphorus, which is the Utah variscite on the sheet. “Variscite” is wrong for any piece with essential copper, and for copper-free material reading 1.5, which fits the faustite, aheylite and planerite rows, or wavellite. The gem society says Neolithic pieces called callaïs, first believed to be turquoise, proved to be variscite.
| Criterion | Variscite | Turquoise | Does it choose? |
|---|---|---|---|
| Formula (IMA) | Al(PO4)(H2O)2 | CuAl6(PO4)4(OH)8(H2O)4 | Yes, by analysis |
| Group (sheet) | Variscite group; series with strengite; dimorphous with metavariscite | Turquoise group; series with chalcosiderite and with planerite | Yes |
| Copper by mass | 0 (no CuO in the Lucin analysis) | 7.81% ideal; 7.19% Lynch Station | Yes for the species; not for the group (faustite, aheylite, planerite have none) |
| Aluminium per phosphorus | 1 ideal; 1.008 Lucin | 1.5 ideal; 1.489 Lynch Station | Yes: the 1-or-1.5 rule |
| Water by mass (ideal) | 22.81% | 17.72% | Only by analysis |
| Crystal system | Orthorhombic, Pcab | Triclinic, P1̄ | Yes, by X-ray; crystals uncommon in both (to 1.5 mm and 3 mm) |
| Refractive indices | α 1.550–1.563; β 1.565–1.588; γ 1.570–1.594 | α 1.61; β 1.62; γ 1.65 | Yes; the gap is worked on the variscite page |
| Optic sign | Biaxial (−) | Biaxial (+) | Yes, with a conoscope on a clear grain |
| Hardness | 4.5 | 5–6 | Yes, but destructive |
| Density; 20.00 g in water | 2.57–2.61; 12.22–12.34 g | 2.86, less if massive; 13.01 g | Usually; porous turquoise reads low |
| Streak | White | White to pale greenish blue | Weakly |
| Colour | Pale green, emerald-green, bluish green, colourless, pale brown or yellow, rarely red | Sky-blue, bluish green, apple-green, greenish grey | No: bluish green is on both lists |
Is variscite a type of turquoise? No: two species, two groups
The IMA list and the sheets. The September 2026 IMA list has separate rows: variscite Al(PO4)(H2O)2, status A, 1967 s.p., Germany; turquoise CuAl6(PO4)4(OH)8(H2O)4, status A, 1967 s.p., country unknown. The variscite sheet puts variscite in the variscite group, dimorphous with metavariscite and in a series with strengite. The turquoise sheet puts turquoise in the turquoise group, in two series, with chalcosiderite and with planerite. Neither sheet names the other mineral.
Same class, different everything else. Both are hydrated aluminium phosphates, which is why they are confused. Turquoise has copper, 7.81% of the ideal formula by mass, and 1.5 aluminium per phosphorus; variscite has neither copper nor hydroxyl in its IMA formula, one aluminium per phosphorus, and 22.81% water against turquoise’s 17.72%. One is orthorhombic, the other triclinic. The separation from variscite’s iron analogue is on strengite vs variscite; this page is about turquoise.
The 1-or-1.5 rule, worked on the sheets’ analyses
Method. Each oxide weight printed in the sheet’s analysis (1) is divided by its molar mass on standard atomic weights. For the variscite from Lucin, Utah (P2O5 44.73, Al2O3 32.40, H2O 22.68, V2O5 0.32, Cr2O3 0.18, Fe2O3 0.06), aluminium per phosphorus is 1.008, and 1.003 if vanadium is counted with phosphorus. For the turquoise from Lynch Station, Virginia (P2O5 34.13, Al2O3 36.50, CuO 9.00, Fe2O3 0.21, H2O 20.12), it is 1.489, and 1.494 with ferric iron; copper comes out at 0.94 per four phosphorus, and 7.19% by mass. The sheet’s own formula for that analysis prints Cu0.95 and Al5.98.
What the rule is for. It reads a laboratory result, not a specimen in the hand. An analysis reporting aluminium and phosphorus near one to one and no copper fits variscite; near 1.5 to 1 with copper fits turquoise. The wavellite page lists the same ideal ratios beside its in-water ladder; this page works them on the two analyses and adds the group test below. Wavellite, at 1.5 and density 2.36, shares turquoise’s ratio, so the rule separates variscite from both but not those two from each other.
Why “it has no copper” is not enough: the turquoise-shape rows
Method. A script over the September 2026 IMA list selected every row whose formula contains (PO4)4(OH)8(H2O)4, or planerite’s (PO3OH)2(OH)8(H2O)4. It found 5: turquoise CuAl6(PO4)4(OH)8(H2O)4; chalcosiderite CuFe3+6(PO4)4(OH)8(H2O)4; faustite ZnAl6(PO4)4(OH)8(H2O)4; aheylite Fe2+Al6(PO4)4(OH)8(H2O)4; and planerite Al6(PO4)2(PO3OH)2(OH)8(H2O)4. This is a count of formulas, not of the turquoise group, which the IMA list does not print.
Documented failure. Three of the five have no copper. So a copper-free result rules out turquoise the species, which is what the question asks, but not the turquoise group: the turquoise sheet puts turquoise in a series with planerite, and faustite is the zinc member discussed on how to tell real turquoise from fake. What the five share is six trivalent cations to four phosphorus, 1.5. Variscite’s 1 is the mark that it belongs to none of them.
How to tell variscite from turquoise without a laboratory
The order. A refractometer reading on a polished surface comes first, and its line is set out as the 1.6 gap on the variscite page. A conoscope on a clear grain gives the sign: variscite biaxial (−), turquoise biaxial (+). Hardness, 4.5 against 5 to 6, marks the piece; see how to test mineral hardness properly. Weight in water is a confirmation, 12.22 to 12.34 g against 13.01 g for 20.00 g. The International Gem Society variscite article warns that common turquoise treatments may mask turquoise’s higher indices, and that variscite passed off as turquoise may be dyed or wax- or polymer-impregnated.
Where neither name fits. The tests for dyed howlite, magnesite and chalcedony are on how to tell real turquoise from fake, chrysocolla’s on is chrysocolla the same as turquoise and howlite’s index on is howlite turquoise. Both sheets name the Iron Monarch quarry, Iron Knob, South Australia, and St Austell, Cornwall, so those labels do not decide. Whether any specimen needs care for chemical reasons, copper-bearing turquoise included, is routed to toxic minerals in a collection; that is not advice. Lamp responses are on is variscite UV reactive. More in the collecting guides. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.