Apatite
Apatite is a group name: fluorapatite, hydroxylapatite and chlorapatite, calcium phosphates of hardness 5, the 5 on Mohs' scale. How to read an apatite label.
Apatite is a group name, not a species. On the September 2026 IMA list it survives in three names, fluorapatite, hydroxylapatite and chlorapatite: calcium phosphates told apart only by fluorine, hydroxyl or chlorine at one site. Hardness 5, the 5 on Mohs' scale; density 3.1 to 3.25. An unanalysed apatite label is most probably fluorapatite.
In short
- No mineral called plain apatite is on the September 2026 IMA-CNMNC Master List. Three rows carry the name: chlorapatite Ca5(PO4)3Cl, fluorapatite Ca5(PO4)3F and hydroxylapatite Ca5(PO4)3(OH), all marked Rn, renamed, 2010 s.p. The 2010 apatite-supergroup report renamed apatite-(CaF), apatite-(CaOH) and apatite-(CaCl) to those three names. A label reading apatite is a group determination.
- One site decides the species: X, at the end of the formula. Fluorine-dominant is fluorapatite, hydroxyl-dominant hydroxylapatite, chlorine-dominant chlorapatite. Dominant means the largest of the three, not a majority: the Handbook’s Fairfax, Virginia chlorapatite has Cl0.48, OH0.29 and F0.23.
- Hardness and density do not separate them. All three sheets give hardness 5 or about 5, and the measured densities overlap: 3.1 to 3.25, 3.14 to 3.21 and 3.17 to 3.18. The fluorapatite sheet calls it the most common rock-forming phosphate mineral; the other two are much less common and relatively much rarer. That is why an unanalysed label most probably means fluorapatite, and why it cannot be certain.
- The supergroup is much wider than the three. Counted by script, 48 rows on the IMA list have the supergroup’s generic formula shape M5(TO4)3X: 22 phosphates, 8 arsenates, 2 vanadates, 6 silicates, 5 sulphates and 5 mixed. Pyromorphite, mimetite and vanadinite are among them.
- Hardness 5 is the apatite step of Mohs’ scale, between fluorite at 4 and feldspar at 6. Of the 168 sheets in this site’s 176-sheet reference set that print a hardness, 23 include 5 in their range and 4 print exactly 5.
| Species | IMA formula | IMA status, year, country | X anion, ideal % by mass | Hardness | Density (measured) | Largest crystals on the sheet |
|---|---|---|---|---|---|---|
| Fluorapatite | Ca5(PO4)3F | Rn; 2010 s.p.; Austria / Germany / Spain / Switzerland | F 3.77% | 5 | 3.1 to 3.25 | To 2 m |
| Hydroxylapatite | Ca5(PO4)3(OH) | Rn; 2010 s.p.; Switzerland | OH 3.39% | 5 | 3.14 to 3.21 | To 30 cm |
| Chlorapatite | Ca5(PO4)3Cl | Rn; 2010 s.p.; Austria / Germany / Spain / Switzerland | Cl 6.81% | About 5 | 3.17 to 3.18 | To 5 cm |
| Pyromorphite | Pb5(PO4)3Cl | G; 1813; Germany | Cl 2.61% | 3.5 to 4 | 7.04 | To 8 cm |
| Mimetite | Pb5(AsO4)3Cl | G; 1832; Germany | Cl 2.38% | 3.5 to 4 | 7.24 | To 12 cm |
| Vanadinite | Pb5(VO4)3Cl | G; 1838; Mexico | Cl 2.50% | 2.5 to 3 | 6.88 | To 14 cm |
Is apatite a mineral? It is a group name with three calcium members
First check: the IMA list. The September 2026 IMA-CNMNC Master List has no row for apatite. A case-insensitive search of the names returns exactly three: chlorapatite, fluorapatite and hydroxylapatite, each with status Rn, renamed, 2010 s.p. The list gives fluorapatite and chlorapatite the country Austria / Germany / Spain / Switzerland, and hydroxylapatite Switzerland, with a first reference in Annales des Mines 10 (1856). Its second reference for fluorapatite and hydroxylapatite is American Mineralogist 103 (2018), 1981.
Second check: the ruling. The 2010 report of the IMA-CNMNC subcommittee, Pasero, Kampf, Ferraris, Pekov, Rakovan and White in European Journal of Mineralogy 22, 163–179, preferred prefixes to suffixes. It renamed apatite-(CaF) to fluorapatite, apatite-(CaOH) to hydroxylapatite and apatite-(CaCl) to chlorapatite, and noted that for the apatite group these changes return the names that have been used in thousands of scientific paper, treatises and museum catalogues over the last 150 years (sic). It also treats clinohydroxylapatite as the monoclinic polymorph of hydroxylapatite, and recognises a monoclinic chlorapatite; the Handbook chlorapatite sheet says end-member chlorapatite is monoclinic.
This page is filed under apatite deliberately, because that is the word on most labels. The axinite and microlite pages treat their group names the same way. The three Handbook sheets used here are not in this site’s 176-sheet reference set; the lead apatites pyromorphite, mimetite and vanadinite are, and their sheets file them under Apatite group.
Fluorapatite, hydroxylapatite or chlorapatite? The X-site rule, worked
The rule: name the specimen for whichever of F, OH or Cl is largest at the X site. It is the name line on each sheet: F > Cl or OH, OH > F or Cl, Cl > F or OH. Worked on the Handbook’s own analyses:
- Gloserheia pegmatite, Froland, Norway: Ca5.00(PO4)2.99F1.03, fluorapatite.
- Holly Springs, Georgia: X = (OH)1.04 F0.08, hydroxylapatite.
- Bob’s Lake, Canada: X = Cl0.91 (OH)0.05 F0.04, chlorapatite.
- Fairfax quarry, Virginia: X = Cl0.48 (OH)0.29 F0.23, still chlorapatite, with chlorine below half the site. Dominant is not the same as majority.
Worked composition. On standard atomic weights the three end-members give P2O5 42.22%, 42.39% and 40.89%, and CaO 55.60%, 55.82% and 53.84%, which reproduces the ideal column on each sheet. Chlorine is 6.81% of chlorapatite by mass, the sheet’s own figure; fluorine is 3.77% of fluorapatite and hydroxyl 3.39% of hydroxylapatite. A difference of a few per cent in one light element is invisible in the hand.
So a label reading apatite should stay a group label until someone has analysed the X site. The sheets’ frequency notes make fluorapatite the likeliest reading, and the honest catalogue entry is apatite (group), probably fluorapatite, with the locality. The form is on how to label and catalogue a mineral collection.
How big is the apatite supergroup? 48 formulas of one shape
The 2010 report gives the generic formula as M12M23(TO4)3X and divides the supergroup into five groups: apatite, hedyphane, belovite, britholite and ellestadite. M can be calcium, lead, barium, strontium, manganese, sodium, cerium, lanthanum, yttrium or bismuth; T is phosphorus, arsenic, vanadium, silicon, sulphur or boron; X is fluorine, hydroxyl or chlorine.
Method. We parsed every row of the September 2026 IMA list by script, rejoining the 78 rows whose formula wraps onto neighbouring lines. We counted formulas with cations totalling 5, then TO4 groups totalling 3, then one X of F, Cl or OH. 48 rows match: 32 approved, 8 renamed, 6 grandfathered and 2 redefined. By T: 22 phosphates, 8 arsenates, 2 vanadates, 6 silicates, 5 sulphates, 4 silicate-sulphates and 1 silicate-phosphate. This is a count of formula shape, not the IMA’s membership list, which the list itself does not record.
Ten of the 48 begin Ca5: the three apatites, svabite, johnbaumite and turneaureite (the arsenates), pliniusite (the vanadate) and the three ellestadites. Seven begin Pb, among them pyromorphite, mimetite and vanadinite. Telling the two commonest lead members apart is on how to tell pyromorphite from mimetite. The lead members are more than twice as heavy as the calcium apatites: measured density 6.88 to 7.24 against 3.1 to 3.25.
Hardness 5: apatite on the Mohs scale and in the reference set
Apatite is the 5 of Mohs’ scale: the USGS lists talc 1, gypsum 2, calcite 3, fluorite 4, apatite 5, feldspar 6, quartz 7, topaz 8, sapphire 9 and diamond 10. The Handbook agrees: fluorapatite and hydroxylapatite 5, chlorapatite about 5, fluorite 4, orthoclase 6 to 6.5. A steel point at about 5.5 sits just above it; the method is on how to test mineral hardness properly.
Across this site’s reference set (hardness field parsed by script, ranges read as ranges): 168 of the 176 sheets print a hardness. 23 include 5 in their range, among them the zeolites analcime, scolecite and mesolite. Four print exactly 5: dioptase, gonnardite, lepidocrocite and mesolite. A green hexagonal prism that scratches at 5 can be apatite or dioptase, and colour and habit have to do the rest.
Fluorescence varies. The fluorapatite sheet says it may be cathodoluminescent, phosphorescent, or fluorescent in UV, without a colour; the hydroxylapatite and chlorapatite sheets say nothing. Background is on fluorescent minerals explained.
Where fine apatite crystals come from, including Panasqueira
The fluorapatite sheet’s Distribution field gives a few of the many localities for fine crystals: Ehrenfriedersdorf, Saxony; Untersulzbachtal, Salzburg; Panasqueira, Portugal; near Pech, Kunar Province, Afghanistan; Chumar Bakhoor, Gilgit district, Pakistan; the Morro Velho gold mine, Minas Gerais; Llallagua, Bolivia; Cerro de Mercado, Durango, Mexico; the Pulsifer quarry, Mt. Apatite, Maine; and large crystals from Renfrew Co., Ontario, and Ottawa Co., Quebec. Its prisms are elongated on [0001] and dominated by {10-10} and {10-11}.
The other two are rarer and differently placed. Hydroxylapatite forms where limestone reacts with phosphatic solutions from guano, in caves worldwide, and in talc schists; its sheet names Chämleten near Hospental, Uri, Switzerland, first. Chlorapatite forms in F-deficient environments; its sheet names large crystals from Snarum, Norway. None of the three sheets names a British locality, and we add none.
Against the 176 sheets in the set, the word apatite appears on 17, and in the Association field of 14. Those 14 include calcite, fluorite, uvite and the scapolite pair. Fluorapatite’s own associates are diopside, forsterite, scapolite, phlogopite, chondrodite, calcite and magnetite. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.