Kunzite
Kunzite is the pink-to-lilac gem variety of spodumene, a lithium aluminum silicate with the formula LiAlSi2O6, colored by trace manganese. It’s a useful stone for illustrating a point that trips people up about gem durability generally: hardness and toughness are not the same property, and a stone can score reasonably on one while being genuinely fragile on the other. See hardness for more on that distinction across gems in general.
Kunzite’s scratch hardness, Mohs 6.5 to 7, is unremarkable — similar to quartz, tougher than many soft ornamental stones. But it has perfect cleavage in two directions, meaning the crystal structure contains planes along which it will split cleanly given the right kind of stress, the way mica sheets peel apart, only less dramatically visible until it happens. A knock that a similarly hard stone without that cleavage would shrug off can crack a kunzite along one of those planes instead. That combination — respectable hardness, poor toughness — makes it a genuinely more demanding stone to cut and set than its Mohs number alone would suggest, and a reason jewelers often recommend protective settings over exposed ones for it.
The other trait worth knowing before buying kunzite is that its color isn’t necessarily permanent. Prolonged exposure to strong light, especially direct sunlight, can fade the pink or lilac color over time — a property sometimes called photosensitivity in colored stones, also seen to varying degrees in some other manganese- or light-sensitive gems. Practically, that means kunzite jewelry is better suited to occasional wear or evening use than to being left in a sunlit display case indefinitely.
Kunzite was named in 1911 after gemologist George Kunz, the same Tiffany & Co. gem buyer who that same year named morganite after banker J. P. Morgan — one gemologist behind two beryl-and-spodumene names in a single year. Afghanistan, Pakistan, and Brazil are leading sources of gem-quality kunzite, with additional material from Madagascar and the United States.
Kunzite doesn’t appear on any of the historical or modern monthly birthstone lists, or on either zodiac system, tracked on this site — it’s included here as a standalone reference entry.
Gemmological properties
| Mohs hardness | 6.5–7 |
|---|---|
| Crystal system | Monoclinic |
| Chemical formula | LiAlSi2O6 |
| Refractive index | 1.66–1.68 |
| Color family | Pink, Purple |
| Variety of | spodumene |
| Also known as | — |
| Origins | Afghanistan, Pakistan, Brazil, Madagascar, United States |
| Organic material | No |
The pink to lilac variety of spodumene, colored by trace manganese. Kunzite has perfect cleavage in two directions, making it genuinely difficult to cut and vulnerable to a sharp knock despite a respectable Mohs 6.5-7 — a clear case of hardness and toughness being different properties. Its color can also fade with prolonged strong light exposure.
Frequently asked questions
- Is kunzite hard enough for everyday jewelry?
- It's a mixed answer. At Mohs 6.5 to 7, its scratch hardness is respectable, similar to quartz. But it has perfect cleavage in two directions, meaning a sharp knock in the wrong spot can split it cleanly, which is a toughness problem rather than a hardness one — the two properties don't move together.
- Why does kunzite's color sometimes fade?
- Its pink-to-lilac color comes from trace manganese, and that color can fade with prolonged exposure to strong light, particularly sunlight. It's generally advised to store kunzite jewelry away from continuous bright light rather than leaving it displayed in a sunny spot.
- Is kunzite a birthstone on any of the lists this site tracks?
- No. It doesn't appear on any of the historical, US, UK, or zodiac systems documented on this site — it's covered here as a standalone gemstone reference entry.