Gem library
Apatite
The deceiver with a neon blue
Apatite lives up to its name: «I deceive». Its palette covers nearly the whole spectrum, and its Madagascan neon blue rivals Paraíba tourmaline visually for a hundredth of the price. A hardness of 5, however, makes it a delicate gem.
- Hardness (Mohs)
- 5
- Density
- 3.16 – 3.23
- Crystal system
- Hexagonal
- Refractive index
- 1.632 – 1.646
- Cleavage
- Imperfect on {0001}
Mineralogical identity
- Family
- Apatite — phosphate group
- Species
- Fluorapatite (also chlor-, hydroxyl-)
- Variety
- Gem apatite
- Chemical formula
- Ca₅(PO₄)₃(F,Cl,OH)
- Crystal system
- Hexagonal
- Classification
- Semi-precious stone
- Rarity
- Common
- Indicative price
- €5 – 60/ct
Etymology
From the Greek apatáō, «I deceive»: Abraham Gottlob Werner named it so in 1786 because it had been confused with almost every other gem — beryl, tourmaline, olivine, amethyst.
Physical & optical properties
- Hardness (Mohs)
- 5
- Density
- 3.16 – 3.23
- Refractive index
- 1.632 – 1.646
- Birefringence
- 0.002 – 0.004
- Cleavage
- Imperfect on {0001}
- Fracture
- Conchoidal to uneven, brittle
- Lustre
- Vitreous to subresinous
- Diaphaneity
- Transparent to translucent
- UV fluorescence
- Strong
- Pleochroism
- Weak
- Colours
- blue, turquoise, green, yellow, violet
Formation, geology & history
The mineral of the living
Apatite is not only a gem: it is the mineral our bones and teeth are made of. Tooth enamel is almost pure hydroxyapatite, and the skeleton of every vertebrate consists of it. It is also the world's main source of phosphorus: the sedimentary apatite deposits of Morocco, China and Russia feed the fertiliser industry, without which modern agriculture would collapse. The stone in your hand therefore belongs to the same mineral species as your jaw, and as the mineral that feeds seven billion people.
A gem at hardness five
Apatite is what defines degree 5 on the Mohs scale: it scratches fluorite and is scratched by orthoclase. Translated into use, that means a knife marks it, sand dulls it, and an apatite ring worn daily will show visible wear within a few years. It is also frankly brittle: conchoidal fracture and low toughness make it a stone that chips at the slightest knock on an edge. Gemmology files it among «collector's stones», a polite term for gems better looked at than worn.
Madagascar's neon blue
Discovered in the 1990s, the electric blue-green of Madagascan apatite is due to manganese and rare earths. Its luminosity immediately recalls Paraíba tourmaline, so much so that it serves as an honesty test for the trade: a seller offering a «Paraíba» at fifty euros a carat is actually selling apatite. Most of these stones are heated to lighten the tone and remove a grey component. The yellow-green apatite of Durango, Mexico, is the other great classic, often cut into remarkably clean stones of ten to thirty carats.
Cat's eye and varieties
Apatite also yields fine chatoyant cabochons, caused by very fine parallel channels: apatite cat's eye, often yellow-green, occurs in Brazil and Madagascar. A violet variety is found in Maine and Germany, and a colourless Sri Lankan apatite was long confused with beryl. Its very low birefringence, around 0.003, clearly separates apatite from tourmaline or zircon on the refractometer.
How to recognise it
- The knife testApatite, at hardness 5, scratches with a steel point — a pocket knife on the girdle, out of sight, is enough. Tourmaline or aquamarine resist absolutely. It is the fastest discriminating test.
- Luminosity without the priceA spectacular neon blue offered at a few tens of euros a carat is apatite. It is a fine stone, but it is not a Paraíba, and an honest seller will tell you so unprompted.
- FluorescenceUnder a UV lamp, many apatites answer with a bright yellow, violet or pink, often livelier than neighbouring gems. A clear UV response on a blue-green stone points to apatite.
Imitations, treatments & confusions
- Apatite sold as Paraíba tourmalineThe usual direction of the fraud. The hardness difference is glaring, and apatite generally shows a hint of grey that Paraíba lacks. On an expensive stone, insist on a certificate.
- Copper glassBlue-green glass imitates the colour but shows round bubbles and too perfect a hue. It does not fluoresce like apatite and feels warm to the touch.
- Undisclosed heated apatiteHeating is common, stable and harmless, but it must be declared. It affects neither strength nor durability: this is a matter of commercial honesty, not quality.
Deposits & origins
Madagascar (exceptional neon blue), Brazil (Minas Gerais), Mexico (Cerro de Mercado, Durango — the classic yellow), Myanmar, Sri Lanka, Canada (Ontario, Quebec), Russia (Kola peninsula, the world's largest deposit), Portugal, Norway
Care & precautions
- Clean with barely soapy warm water and a soft cloth only. Quick rinse, immediate drying.
- Never ultrasonic, never steam: apatite is among the gems most vulnerable to vibration and thermal shock.
- It fears all acids, even weak ones — vinegar, lemon juice, household products, prolonged perspiration.
- Reserve it for pendants, brooches and earrings; in a ring, use a closed setting and occasional wear.
Traditions & crystal healing
- Chakras
- Throat · third eye
- Zodiac signs
- Gemini · Aquarius
- Element
- Air · Water
- Month
- May
Crystal healing links blue apatite to the throat and to expression: a stone of speakers and teachers, said to support clear speech and self-assertion. Its kinship with bone tissue has earned it, by analogy, a reputation as a stone of structure and rebuilding — a symbolic argument, not a medical one.
The virtues described here belong to tradition and cultural heritage. They are in no way medical advice and never replace a consultation.
Frequently asked questions
Can apatite be worn in a ring?
It is inadvisable for daily wear: at hardness 5 it is scratched by sand and marked by a knife, and its brittleness makes it knock-sensitive. In an evening ring with a protective setting, yes.
Apatite or Paraíba tourmaline?
Hardness settles it immediately: apatite scratches with steel, tourmaline does not. So does price — a factor of fifty to a hundred. A neon blue apatite is an excellent stone, provided it is sold under its own name.
Can it go in water?
A brief rinse is fine, but avoid soaking, salt water and anything acidic. Apatite is a phosphate: acids genuinely attack it, unlike quartz.