How Tanzanite and Sapphire differ in what they are, color, hardness and care.
| Tanzanite | Sapphire | |
|---|---|---|
| What it is | The blue violet variety of the mineral zoisite, found only in Tanzania near Mount Kilimanjaro. It was discovered in 1967. | A variety of the mineral corundum (the same mineral as ruby), known for its hardness and its wide range of colors. |
| Birthstone for | December | September |
| Colors | Pale blue to intense ultramarine with violet undertones; Shows different colors from different angles | Blue (the classic color); White; Pink; Orange; Yellow; Green; Violet; Purple; Brown; Black; Padparadscha (pink and orange) |
| Mohs hardness | 6 to 7 | 9 |
| Toughness | Fair to poor. It has cleavage and can break if struck. | Excellent, with no cleavage; does not tend to break when struck. |
| Everyday wear | Wear with care | Great for everyday rings |
| Ultrasonic cleaner | Never | Usually safe for untreated, heated and lattice diffusion treated stones; not for filled or dyed stones |
| Main sources | Tanzania only (a few square miles near Mount Kilimanjaro) | Not stated |
| Common treatments | Routinely heat treated to turn brownish crystals blue or violet; this is stable. | Untreated and heat treated sapphire is very durable. Clean fracture filled, cavity filled or dyed stones only with a damp cloth. |
Sapphire is the harder of the two (9 on the Mohs scale). Choose by the color you love and how the piece will be worn; for a ring worn every day, the tougher stone will last better.
Sources: GIA: Tanzanite care and cleaning, AGS: Tanzanite, GIA: Sapphire care and cleaning, AGS: September birthstone. Checked October 16, 2026.
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