How Much Is Andalusite Worth?
An affordable collector’s gem with a party trick — strong pleochroism that flashes green and reddish-brown from a single stone, so the cut and the colour play, not the carat, set the price.
Andalusite is a connoisseur’s gem that has never gone mainstream, and that is part of its charm — and its value. Chemically it is aluminium silicate, sharing the exact formula of kyanite and sillimanite while being a distinct mineral formed at different pressures and temperatures. Named after Andalusia in Spain, it comes in earthy greens, browns and reddish tones, but its real signature is pleochroism: look into a cut andalusite and it flashes different colours — typically green and reddish-brown — as you turn it, sometimes showing both at once in a single face.
That colour play, not the body colour alone, is what a good andalusite is about. It is hard and durable enough for everyday jewellery, it is almost always sold natural and untreated, and it stays affordable because it is a niche stone rather than a household name. The prize is a clean, well-cut stone whose facets are oriented to show lively, contrasting green-and-red pleochroism; a dull, muddy brown stone with weak colour separation is ordinary. There is also a famous variety, chiastolite, whose dark cross-shaped inclusions make it a curiosity in its own right — so knowing what drives value across faceted gems and cross stones is the key to buying andalusite well.
Key takeaways
- Pleochroism is the value. Lively, contrasting green-and-red colour play from a single stone is what you are really paying for.
- Cut does the work. A cutter orients andalusite to capture two colours at once; a well-cut stone is worth far more than a dull, muddy one of the same weight.
- It is hard-wearing and untreated. At Mohs 7–7.5 and almost always natural, it holds up in daily jewellery — a genuine plus in a treated market.
- It stays affordable. As a niche collector gem, even fine andalusite is modestly priced next to mainstream stones of similar quality.
- Chiastolite is a different buy. The cross-stone variety is valued for a crisp, well-centred dark cross, not for colour play, and is priced by the piece.
What andalusite actually is
Andalusite is an aluminium nesosilicate — aluminium silicate — and one of three minerals that share that same composition, alongside kyanite and sillimanite; each forms under different conditions of pressure and temperature, which is why geologists prize the trio as indicators of how rocks formed. Gem andalusite is transparent and typically ranges through brownish-green, yellowish-green, olive and reddish-brown. Its defining optical property is strong pleochroism (technically trichroism): the crystal absorbs light differently along different directions, so it shows distinct colours — often green and reddish-brown — depending on the angle you view it from.
On the Mohs scale it sits around 7 to 7.5, hard enough for rings, pendants and daily wear, and it is almost always sold natural, without the heat or irradiation common in other gems. Gem-quality material comes chiefly from Brazil and Sri Lanka, with Spain — the source of the name — and other localities adding specimens, while vast low-grade deposits are mined industrially as a refractory rather than cut as gems. The opaque chiastolite variety contains dark carbon or clay inclusions arranged in a cross shape that appears when the crystal is sliced across, giving the “cross stone” long used as an amulet. For a comparison with another brilliant, characterful collector gem, see our guide to sphene.
How it is valued
Colour play leads. The most valued faceted andalusite shows strong, lively pleochroism — clear, contrasting green and reddish-brown, ideally visible together in a single stone rather than a muddy blend. Clarity matters, since eye-clean stones command more than included ones, and cut is decisive: because the colours depend on crystal direction, a skilled cutter orients the gem to capture the best colour play, and a well-cut stone far outperforms a poorly oriented one of equal weight. Size lifts price too, as clean, strongly pleochroic material above a couple of carats is scarcer. The chiastolite variety is judged differently — on a crisp, well-centred, high-contrast cross — and is sold by the piece. To see how professionals weigh colour, clarity and cut, read our guide to how gemstones are graded.
Typical fair prices
| Grade | Indicative fair price | Notes |
|---|---|---|
| Small commercial faceted | $10–$40 per carat | Under ~1 ct, modest or muddy colour play |
| Clean, lively colour play | $40–$150 per carat | Eye-clean, clear green-and-red pleochroism |
| Large, fine, dramatic gem | $150–$400+ per carat | Bigger, clean, strongly pleochroic and well cut |
| Chiastolite cross stone | Priced by the piece | Valued for a crisp, well-centred dark cross |
These are Fair Carat’s synthesis of observed dealer listings, not survey data. Faceted andalusite is priced by the carat, while chiastolite cross stones are sold by the piece; either way, colour play, clarity and cut — not sheer weight — do most of the work in setting value, and its untreated, hard-wearing nature is part of the appeal.
Watch-outs
- Dull, muddy colour. Stones with weak, brownish colour play and no clear green-and-red separation are ordinary; the premium sits with lively, contrasting pleochroism.
- Poor orientation. A badly cut stone hides the colour play or shows a murky mix; well-oriented cutting is what makes andalusite sing, so judge the face-up colours carefully.
- Confusion with other gems. Brownish-green andalusite is sometimes mixed up with tourmaline, sphene or even chrome diopside; ask for the identification, especially at higher prices.
- Chiastolite quality. A faint, off-centre or broken cross is worth little; look for a crisp, well-centred, high-contrast cross in the cross-stone variety.
- Marketing hype. “Grounding” and problem-solving claims are folklore, not a reason to pay more — see our look at gemstones as an investment.
For the mineralogy of andalusite, its aluminium-silicate polymorphs and its strong pleochroism, see the GIA gem encyclopedia and Wikipedia. Because andalusite is prized for being natural, our guide to natural versus lab-grown gemstones and to reading a lab report are useful companions.
Chase lively green-and-red colour play in a clean, well-cut stone.
The best faceted andalusite shows strong, contrasting pleochroism — clear green and reddish-brown, ideally together — in an eye-clean, well-oriented stone. Favour skilled cutting over sheer size, enjoy that it is hard-wearing and untreated, and for chiastolite look for a crisp, well-centred cross.
Browse andalusite at Minerals Kingdom →
FAQ
Is andalusite valuable?
It is affordable for a genuine collector gem. Small commercial stones cost a few tens of dollars per carat, while clean, strongly pleochroic material runs higher, and large fine gems higher still — but andalusite stays modestly priced next to mainstream stones of similar quality because it is niche. A first-rate, lively stone is a real find for the money.
What makes andalusite change colour?
Strong pleochroism. The crystal absorbs light differently along different directions, so it shows distinct colours — usually green and reddish-brown — depending on the viewing angle, and a well-cut stone can display both at once. It is not colour-change in the alexandrite sense (which shifts with lighting); it is the same stone showing different colours from different directions.
Is andalusite the same as kyanite?
No, though they share the exact chemical formula. Andalusite, kyanite and sillimanite are three separate minerals with the same aluminium-silicate composition, each formed under different pressure and temperature. They look and behave differently as gems, so andalusite’s green-and-red pleochroism is quite distinct from kyanite’s blue.
Is andalusite hard enough for a ring?
Yes. At about Mohs 7 to 7.5 it is durable enough for rings, pendants and everyday wear, comparable to quartz and harder than many coloured stones. Sensible care still helps — avoid hard knocks and abrasive grit — but it is one of the more wearable collector gems, and it is almost always untreated.
What is chiastolite?
Chiastolite is a variety of andalusite containing dark carbon or clay inclusions arranged so that a cross shape appears when the crystal is cut across. Long worn as a “cross stone” amulet, it is opaque and valued for a crisp, well-centred, high-contrast cross rather than for colour play, and it is sold by the piece.
Where does andalusite come from?
Gem material comes mainly from Brazil and Sri Lanka, with Spain — the source of the name, after Andalusia — and other localities adding specimens. Enormous low-grade deposits are also mined industrially as a heat-resistant refractory, but that material is not gem quality; the cuttable stones are the scarcer, cleaner pockets.
More value guides
Sources
GIA gem encyclopedia — andalusite, its aluminium-silicate polymorphs and pleochroism. Wikipedia — andalusite composition, the chiastolite variety and localities. Observed dealer listings for the price data points. All price figures are indicative Fair Carat synthesis, not survey data.
Independent gem-value research. We don’t sell stones and sellers can’t buy a better verdict.
Informational only — not a formal appraisal. For insurance or resale, get a certified appraisal.