Is Tanzanite hard enough for everyday rings?

Not ideally. At a Mohs hardness of 6.5–7, Tanzanite is soft enough to scratch with everyday wear, so it is better suited to earrings, pendants, or occasional-wear rings with protective settings.

How can I tell Tanzanite from sapphire?

Tanzanite and sapphire can look alike to the naked eye, but they differ in measurable properties — refractive index (1.691–1.7 for Tanzanite), specific gravity (3.1–3.38), and hardness (Mohs 6.5–7). A gemologist confirms the distinction with a refractometer and loupe; the Jewelry Identifier app gives a fast first read from a photo.

Does Tanzanite come in colors other than blue?

Yes. Tanzanite occurs in blue, violet, blue-violet (trichroic). Color is driven by trace elements and treatment history, and it is one of the biggest factors in a stone's value.

* zoisite gemstone

Tanzanite: identification, value, and how to spot a fake

Blue zoisite from Tanzania, discovered 1967. Mined from a single small area near Mount Kilimanjaro — limited geographic supply. Most market tanzanite is heat-treated to enhance blue. Strong pleochroism (color shift by viewing angle).

Published May 30, 2026

Quick facts

Mineral family: zoisite
Chemical formula: Ca2Al3(SiO4)3(OH)
Mohs hardness: 6.5–7
Refractive index: 1.691–1.7
Specific gravity: 3.1–3.38
Crystal system: orthorhombic
Luster: vitreous
Birthstone month: December

Colors

Tanzanite is found in blue, violet, blue-violet (trichroic). The body color, its saturation, and how evenly it spreads through the stone are among the strongest drivers of value.

How to tell real from imitation

No single test settles it, but a few grounded checks quickly narrow things down for Tanzanite. Hardness, brilliance, and the list of stones it is commonly confused with all give you something concrete to look for.

Scratch resistance: genuine Tanzanite sits at Mohs 6.5–7, so it should resist scratching from softer materials — a stone that mars far too easily is suspect.
Brilliance & luster: Tanzanite shows a vitreous luster and a refractive index of 1.691–1.7; imitations often look glassier or flatter under the same light.
Density: a real Tanzanite has a specific gravity near 3.1–3.38, so it feels heavier or lighter in the hand than many look-alikes of the same size.
Commonly imitated by: sapphire, iolite, synthetic forsterite. If a deal looks too good, suspect one of these substitutes first.
Fast first read: photograph the stone in the Jewelry Identifier app to estimate the gemstone and its likely value range, then confirm anything important with a gemological lab.

Common treatments

heat treatment (near-universal)

Treatments are routine for many Tanzanite stones, but they materially affect value and should always be disclosed — an untreated, lab-certified stone commands a clear premium over a treated one.

What to know about Tanzanite

Sources

Wikidata Q424428

* Frequently asked

FAQ

Q. Is Tanzanite hard enough for everyday rings?: A. Not ideally. At a Mohs hardness of 6.5–7, Tanzanite is soft enough to scratch with everyday wear, so it is better suited to earrings, pendants, or occasional-wear rings with protective settings.
Q. How can I tell Tanzanite from sapphire?: A. Tanzanite and sapphire can look alike to the naked eye, but they differ in measurable properties — refractive index (1.691–1.7 for Tanzanite), specific gravity (3.1–3.38), and hardness (Mohs 6.5–7). A gemologist confirms the distinction with a refractometer and loupe; the Jewelry Identifier app gives a fast first read from a photo.
Q. Does Tanzanite come in colors other than blue?: A. Yes. Tanzanite occurs in blue, violet, blue-violet (trichroic). Color is driven by trace elements and treatment history, and it is one of the biggest factors in a stone's value.

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