Is fluorite a quartz?
Is fluorite a quartz? No: fluorite is CaF2, cubic, hardness 4, density 3.175–3.184; quartz is SiO2, hardness 7, density 2.65. The two share no chemical element.
No. Fluorite is calcium fluoride, CaF2: cubic, hardness 4, density 3.175 to 3.184, with one refractive index, 1.433 to 1.448. Quartz is silicon dioxide, SiO2: hexagonal, hardness 7, density 2.65, with two indices, 1.544 and 1.553. The two formulas share no element. Fluorite is a mineral in its own right and forms crystals.
In short
- The verdict. Fluorite is not a kind of quartz. The September 2026 IMA-CNMNC Master List has separate rows: fluorite CaF2, status G; quartz SiO2, status A, 1967 s.p. The Handbook of Mineralogy sheets put fluorite at hardness 4 and density 3.175 to 3.184, quartz at 7 and 2.65.
- The no-shared-element check. Worked on standard atomic weights, CaF2 is 51.33% calcium and 48.67% fluorine, the figures in the fluorite sheet’s ideal column; SiO2 is 46.74% silicon and 53.26% oxygen. Not one element is common to both. The fluorite sheet’s Corvara, Italy, analysis carries 0.05% SiO2, which is 0.023% silicon.
- The one-index test. The fluorite sheet prints isotropic with weak anomalous anisotropism, n 1.433 to 1.448: one index. The quartz sheet prints uniaxial (+), ω 1.544 and ε 1.553: two. The lowest quartz index is 0.096 above the highest fluorite index.
- Documented failure: colour. Of the 11 colour words on the fluorite sheet, 9 also appear on the quartz sheet’s colour line, counted by script; only purple and orange do not, and quartz lists bluish violet. Each sheet names the other among its associates, so the two can share a specimen. Colour and company prove nothing.
- Mineral and crystal. Fluorite is a mineral: it has its own IMA row and its sheet records cubes and octahedra to 2 m. The weight-in-water filter for real fluorite is on how to tell if fluorite is real; fluorite against the word fluoride is on is fluorite the same as fluoride.
| Property | Fluorite | Quartz | Separates? |
|---|---|---|---|
| Formula (IMA); status | CaF2; G | SiO2; A, 1967 s.p. | Yes |
| Elements by mass, worked | Ca 51.33%, F 48.67% | Si 46.74%, O 53.26% | Yes: no element in common |
| Crystal system; cell density worked | Cubic, Fm3m, a 5.4626 Å, Z = 4: 3.181 (printed 3.180) | Hexagonal, a 4.9135, c 5.4050 Å, Z = 3: 2.649 (printed 2.66) | Yes, when crystals show |
| Optical class and refractive index | Isotropic; n 1.433–1.448 | Uniaxial (+); ω 1.544, ε 1.553 | Yes: one index against two, 0.096 apart |
| Hardness (Mohs) | 4 | 7 | Yes: 3 steps |
| Density, measured | 3.175–3.184 | 2.65; 2.59–2.63 massive | Yes |
| 20.00 g piece in water | 13.70–13.72 g | 12.45 g | Yes, on a 0.01 g scale |
| Cleavage | {111} perfect | Rarely observable; conchoidal fracture | Yes, on a broken edge |
| Colour words on the sheet (script) | 11, from colourless to bluish black | 9 of fluorite’s 11 also present | No |
| Associates | Quartz listed first | Fluorite listed second | No |
Is fluorite a type of quartz?
No: different formula, different elements, different crystal system. Fluorite is calcium fluoride, CaF2, and quartz is silicon dioxide, SiO2. On the September 2026 IMA list fluorite is status G with its year printed as “?” and its country unknown; quartz is status A, 1967 s.p., country unknown. A field scan of the IMA formula column finds one row written CaF2, fluorite, and eight written SiO2, which is quartz a mineral lists.
The no-shared-element check, worked. On standard atomic weights CaF2 has a formula mass of 78.07: calcium 51.33%, fluorine 48.67%, exactly the fluorite sheet’s ideal column. SiO2 is 60.08: silicon 46.74%, oxygen 53.26%. Neither formula contains an element of the other. The fluorite sheet’s one analysis, from Corvara, Trentino-Alto Adige, has Ca 51.24, F 48.29, SiO2 0.05, MgO 0.03 and LOI 0.22: the silica is 0.023% silicon, an impurity level.
Different families on the sheets. The fluorite sheet gives cubic, point group 4/m 3̄ 2/m; cubes, octahedra, rarely dodecahedra, to 2 m; cleavage {111} perfect, with a poor parting on {011}. The quartz sheet gives hexagonal, point group 32; prismatic crystals to 6 m; cleavage rarely observable; fracture conchoidal; and names cristobalite, tridymite, coesite and stishovite as its polymorphs. None of that applies to fluorite.
How to tell fluorite from quartz: the one-index test
One refractive index or two. The fluorite sheet prints “Isotropic; weak anomalous anisotropism”, n = 1.433 to 1.448: light travels at one speed whatever the direction. The quartz sheet prints “Uniaxial (+)”, ω = 1.544, ε = 1.553: two indices, 0.009 apart. On a refractometer, a single reading at or below 1.448 is the fluorite reading; two readings near 1.544 and 1.553 are the quartz reading. The gap between the two minerals’ nearest indices is 0.096.
Without a refractometer. Hardness 4 against 7 is three Mohs steps: steel marks fluorite and not quartz, on the method at how to test mineral hardness properly. A clean 20.00 g piece reads 13.70 to 13.72 g in water as fluorite and 12.45 g as quartz, the figures on fluorite and quartz; the weighing method is on how to measure specific gravity at home. The full five-check sequence for fluorite, with the look-alikes, is how to tell if fluorite is real and is not repeated here.
On a broken edge. Fluorite’s perfect {111} cleavage leaves flat, bright, triangular breaks; quartz breaks with a curved, conchoidal fracture. The geometry of fluorite’s break is on why did my fluorite break, and the general distinction on cleavage or fracture.
Why do people mix up fluorite and quartz?
Colour. Counted by script over the two colour lines, 9 of the 11 colour words on the fluorite sheet also appear on the quartz sheet: colourless, white, blue, green, yellow, red, pink, brown and black (as rose-red, rose-pink and brown to black on quartz). Purple and orange are on the fluorite line only, and quartz lists bluish violet. A purple or green crystal is not identified by its colour; for purple quartz, see how to tell if amethyst is real.
They grow together. The fluorite sheet lists quartz first among its associates, and the quartz sheet lists fluorite second. A specimen of one on the other is two minerals, and each needs its own check.
Documented failure: the glow. The fluorite sheet says it fluoresces blue, violet, green, yellow or red under UV and may be phosphorescent, thermoluminescent or triboluminescent; the quartz sheet’s one luminescence entry is that it may be triboluminescent. That sounds like a test, but the fluorite sheet names no UV band, so on its own wording a dark result under one lamp is not a negative. The question is set out on is fluorite UV reactive.
Is fluorite a mineral? Is fluorite a crystal?
A mineral: yes. Fluorite has its own row on the IMA list, CaF2, status G, which marks a species described before the IMA was founded and generally considered valid. Nickel (1995) defines a mineral in general terms as an element or chemical compound that is normally crystalline and formed as a result of geological processes. The definition test itself, worked on quartz, is on is quartz a mineral.
A crystal: usually, as specimens go. The fluorite sheet records cubes, octahedra, rarely dodecahedra, rounded or stepped, to 2 m, and also nodular, botryoidal, granular and massive forms. Crystalline means an ordered internal structure, which fluorite has (space group Fm3m, a 5.4626 Å); whether a given piece shows crystal faces is another matter. The two words are separated on crystal vs mineral.
Other “is it a quartz” questions. Is celestite a quartz, is topaz a quartz and how to tell calcite from quartz work through other minerals mistaken for quartz. 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.