Is apatite fluorescent
Often. The fluorapatite sheet says it may fluoresce in UV. Manganese gives yellow, rare earths blue, white or pink (Modreski 1987); a crystal can glow in bands.
Is apatite fluorescent? Often, not always. The Handbook fluorapatite sheet says it may be fluorescent in UV; the hydroxylapatite and chlorapatite sheets record none. Modreski (1987) calls apatite a common fluorescent mineral: manganese, Mn2+, gives yellow and rare earths blue, white or pink. The colour depends on the specimen, and a dark result under a 254 nm shortwave lamp proves nothing.
In short
- The Handbook says may, and only for one of the three. The fluorapatite sheet reads may be cathodoluminescent, phosphorescent, or fluorescent in UV. The hydroxylapatite and chlorapatite sheets record no luminescence. Apatite is a group name; an unanalysed apatite is most probably fluorapatite, as the species page explains.
- Modreski's rule: apatite is variably fluorescent, depending on what is in it. Writing in New Mexico Geology in 1987, the USGS mineralogist Peter Modreski grouped apatite with fluorite and calcite as variably fluorescent. Activators such as Mn2+ cause it, and quenchers such as Fe2+, Cu2+ or Ni2+ destroy it. In apatite, Mn2+ gives yellow and rare-earth ions blue, white or pink.
- The body-colour key ties the glow to the stone's own colour. The International Gem Society says yellow apatites fluoresce lilac-pink, blue ones violet-blue to sky blue, violet ones greenish-yellow under longwave or pale mauve under shortwave, and green ones a greenish mustard. The table sets them against Modreski's activators.
- One crystal can answer yes and no. Knutson, Peacor and Kelly (1985) found the Panasqueira apatites luminesce yellow-orange under shortwave UV, in concentric growth zones. Of three zones in one crystal that they analysed for UV absorption, two luminesced and one did not. A dark band on an apatite is a zone, not a fault.
- Counted over the eight sheets compared here, three apatites and five tourmalines, three print fluorescence: fluorapatite, dravite and uvite, the two tourmalines only weakly. A bright glow therefore favours apatite over tourmaline, but no glow proves nothing.
| Apatite as seen in daylight | Fluorescence reported | Lamp | Cause reported | Source |
|---|---|---|---|---|
| Yellow | Lilac-pink | SW and LW, stronger LW | Pink glow, in general: rare-earth combinations (Modreski) | IGS; Modreski |
| Blue | Violet-blue to sky blue | Not stated | Blue glow, in general: rare-earth combinations (Modreski) | IGS; Modreski |
| Violet | Greenish-yellow; pale mauve | LW; SW | Not stated | IGS |
| Green | Greenish mustard | Stronger LW than SW | Not stated | IGS |
| Green to colourless, Panasqueira, Portugal | Yellow-orange, zoned; four bands, 349, 445, 555 and 701 nm | SW, mercury lamp | 555 nm band: Mn2+, sensitised by Eu2+ and Ce3+; 349 nm Ce3+; 445 nm Eu2+ | Knutson et al. 1985 |
| Gray-white to bluish-gray, Harding pegmatite, New Mexico | Yellow | SW | Predominantly Mn2+ | Modreski, Fig. 16 |
| Copper Flat porphyry copper deposit, New Mexico | Pinkish-white | SW | Not stated | Modreski |
| Manganapatite (a variety name, not an IMA species) | Pink | SW | IGS: manganese. Modreski: Mn2+ gives yellow | IGS; Modreski |
Is apatite fluorescent? What the three Handbook sheets say
Apatite is often fluorescent, but no Handbook sheet promises it: fluorapatite's says may, and the other two say nothing. The Handbook of Mineralogy sheet for fluorapatite reads may be cathodoluminescent, phosphorescent, or fluorescent in UV, with no colour. The hydroxylapatite and chlorapatite sheets carry no luminescence statement. That matches the apatite species page, which explains why an unanalysed apatite is most probably fluorapatite.
Method. Eight sheets were converted with pdftotext -layout and searched by script, case-insensitively, for fluoresc-, with the fl allowed to come out as a stray glyph, as it does on older sheets. The positive controls, hemimorphite and willemite, both matched. The eight are the three calcium apatites and five tourmalines, schorl, elbaite, dravite, uvite and liddicoatite, because the International Gem Society says faceted apatite and tourmaline can be hard to separate. Three of the eight print fluorescence: fluorapatite; dravite, may weakly fluoresce under SW UV; and uvite, a weak mustard-yellow under SW UV.
So the definition is conditional. Yes, apatite is a fluorescent mineral in the sense that much of it glows; no, it is not fluorescent in the way that, on Modreski's account, scheelite and autunite are always or nearly always fluorescent. Background on why some minerals glow is on fluorescent minerals explained, and the fluorescence pages are indexed at the collecting guides.
What colour does apatite glow under UV? The body-colour key
The colour of the glow follows the chemistry, and the stone's daylight colour is a rough guide to it. Peter Modreski's 1987 review in New Mexico Geology gives the chemistry: apatite's fluorescence is due either to Mn2+, giving yellow, or to combinations of rare-earth elements including Eu2+, Ce3+, Sm3+ and Dy3+, giving blue, white or pink. He calls yellow-fluorescent apatite typical of many pegmatitic apatites. The International Gem Society gives the body-colour side: yellow apatite glows lilac-pink, blue apatite violet-blue to sky blue, violet apatite greenish-yellow or pale mauve, green apatite a greenish mustard.
A documented disagreement: what pink means. The IGS says manganapatite, a variety in which manganese replaces calcium, fluoresces pink under shortwave UV. Modreski attributes pink to rare earths and yellow to Mn2+. Both are published sources; we print both and choose neither. In our judgement the safe reading is that the colour of the glow does not identify the activator without analysis.
Shortwave or longwave? Modreski defines shortwave UV by the 254 nm mercury line and longwave by a strong component near 365 nm. The IGS says apatite fluoresces under both, with its yellow and green apatites stronger under longwave. A torch-or-lamp comparison is on UV torch or lamp for minerals. This page gives no safety advice.
Why one apatite crystal can glow in bands: Panasqueira
A single Panasqueira apatite can be fluorescent in one growth zone and dark in the next. Knutson, Peacor and Kelly, in American Mineralogist in 1985, studied the green to colourless apatites from the tin-tungsten veins of Panasqueira, Portugal. They describe concentric growth zoning shown by colour, fission-track density and luminescence intensity, and a yellow-orange luminescence with four emission bands, at 349, 445, 555 and 701 nm, excited with shortwave UV.
Their activators. They propose cerium (Ce3+) for the 349 nm band, europium (Eu2+) for 445 nm, and manganese (Mn2+) sensitised by Eu2+ and Ce3+ for 555 nm; the 701 nm band's cause was unknown. Of three zones in their test crystal analysed for absorption, two were luminescent and one without luminescence. Crystals from the same vug showed strikingly similar zone sequences, but they could correlate them over only about ten metres.
What that means for a collector. A dim or banded glow is not a sign of a fake or of damage. The International Gem Society's photograph of a Panasqueira fluorapatite shows the same thing: green zones fluorescing yellow and colourless zones blue-white. The fluorapatite sheet names Panasqueira among a few of the many localities for fine crystals.
Can a UV lamp tell apatite from tourmaline?
Only in one direction: a strong glow favours apatite, because the International Gem Society says tourmalines are usually weak to inert in UV light. On the sheets compared here, only dravite and uvite mention fluorescence, both weak and under shortwave. The IGS does note exceptions, such as tourmalines from Newry, Maine, that may be chalky blue to strong blue under shortwave, and Tanzanian stones that are strong yellow.
No glow proves nothing, for either mineral. Modreski's quenchers, such as ferrous iron, can suppress fluorescence in material that would otherwise glow. Hardness is the cleaner field test on rough: apatite is 5 on its sheets, tourmaline 7 to 7.5. On a cut stone, the refractometer gap is the better test, as set out on how to tell if tourmaline is real.
Other fluorescent minerals often found with apatite include calcite, which the fluorapatite sheet lists as an associate; how calcite glows is on is calcite UV reactive. Nothing on this site is offered for sale; the wanted list is the only commercial route.