Is scheelite fluorescent?
Yes, under shortwave: its Handbook sheet records bright bluish white under SW UV. Molybdenum moves the glow from blue to yellow; past 5 wt% Mo all looks yellow.
Yes, under shortwave. The Handbook of Mineralogy sheet records bright bluish white fluorescence under SW UV and names no longwave response; the International Gem Society gives longwave as inert or dull yellow. Modreski (1987) found nearly all scheelite fluorescent, the glow moving from blue to yellow as molybdenum rises, and equally yellow above about 5 wt% Mo.
In short
- The sheet’s words. The Handbook scheelite sheet reads Bright bluish white cathodoluminescence and fluorescence under SW UV and X-rays. There is no may before it, and no longwave response is named. The International Gem Society scheelite panel adds: in LW, inert or dull yellow (Sri Lanka).
- The molybdenum ladder. Modreski (New Mexico Geology, 1987) used a 12-sample comparator card for the scheelite–powellite series: under 0.05 wt% Mo the scheelite glowed blue, at about 0.7 wt% white, and above 5 wt% yellow. Above that amount, he says, everything appears equally yellow and the card cannot tell compositions apart. Converted by script, 0.15, 2 and 14 mole% powellite are 0.05, 0.67 and 4.87 wt% Mo, matching his paired figures.
- Colour in daylight does not predict the glow. Modreski’s Ortiz mine crystal was orange in normal light and fluoresced white under shortwave; his Irish Rose mine scheelite, rimming wolframite, fluoresced blue. The gem society records a scheelite with probable molybdenum glowing yellowish.
- Half the family, by script. Read ligature-aware, with hemimorphite and willemite as positive controls, 3 of 6 tungstate and molybdate sheets record fluorescence: scheelite (SW), powellite (SW) and stolzite (LW and SW). Wulfenite, ferberite and hübnerite record none.
- Where yes stops meaning natural. The gem society says synthetic scheelite generally fluoresces blue to blue-white under shortwave, some red to orange-red under longwave, and pale green synthetics pink. Shortwave lamps carry the tighter ICNIRP 2004 weighting; this page is not safety advice.
| Material | Source | Mo content | Shortwave (254 nm) | Longwave (365 nm) |
|---|---|---|---|---|
| Scheelite | Handbook sheet | Not stated | Bright bluish white (and X-rays) | Not named |
| Scheelite | IGS panel | Not stated | Brilliant bluish white or whitish blue; some yellow | Inert or dull yellow (Sri Lanka) |
| Scheelite, Irish Rose mine, New Mexico | Modreski, Fig. 6 | Under 0.05 wt% (under 0.15 mole% powellite) | Blue | Not reported |
| Scheelite, Ortiz mine, New Mexico (orange in daylight) | Modreski, Fig. 7 | About 0.7 wt% (2 mole%); worked 0.67 | White | Not reported |
| Powellite–scheelite, Iron Mountain No. 2 mine | Modreski, text and Fig. 8 | Over 5 wt% (over 14 mole%); about 50 mole% CaMoO4, worked 19.66 wt% | Yellow | Not reported |
| Molybdenum-bearing scheelite (molybdoscheelite) | IGS article | Some Mo | Creamy yellow | Not stated |
| Powellite | Handbook sheet | Ca(MoO4) | Creamy white or yellow to golden yellow | Not named |
| Powellite | IGS article | Ca(MoO4) | Yellowish to golden yellow | Yellowish to golden yellow |
| Synthetic scheelite | IGS article | Rare-earth dopants | Blue to blue-white; pale green synthetics pink | Some red to orange-red |
| Stolzite, Pb(WO4) | Handbook sheet | None | May fluoresce lemon-yellow | May fluoresce bright red to red-orange |
| Wulfenite, ferberite, hübnerite | Handbook sheets | — | Nothing recorded | Nothing recorded |
Does scheelite glow under UV light? What the sheet says
Scheelite fluoresces bright bluish white under shortwave on its Handbook sheet, and the sheet names no longwave response. The full line on the Handbook of Mineralogy scheelite sheet is Bright bluish white cathodoluminescence and fluorescence under SW UV and X-rays. Cathodoluminescence is a response to an electron beam, a laboratory effect.
What sits outside that line. The International Gem Society records longwave as inert or dull yellow (Sri Lanka), says scheelite also shows thermoluminescence, and calls the shortwave response extremely bright. Modreski (New Mexico Geology, 1987) says a few minerals, such as scheelite and autunite, are always or nearly always fluorescent because of ions or groups present intrinsically, and that nearly all scheelite fluoresces through luminescence from the tungstate ion. That is a cause he states for the species, not a trace activator.
How the sheets were read. The search was fl or any single non-letter, followed by uoresc, case-insensitive, because older sheets render the fl ligature as a stray glyph. Hemimorphite and willemite are the positive controls; both match, and a literal search matches neither. The scheelite sheet itself prints the word plainly. Species data are on scheelite.
Why does some scheelite glow yellow? The molybdenum ladder
The molybdenum ladder: in Modreski’s 1987 comparison, scheelite under 0.05 wt% Mo glowed blue, scheelite at about 0.7 wt% glowed white, and material over 5 wt% glowed yellow, and above that amount every composition looked equally yellow. He describes the colour as varying in a predictable way, from blue for pure tungsten scheelite through bluish white, white and yellowish white to yellow with increasing Mo, and a comparator card of 12 calibrated powders in the scheelite–powellite series made for estimating the molybdenum content of scheelite ores.
Worked check. Modreski gives each figure twice, as weight per cent Mo and as mole per cent powellite. Converting on standard atomic weights for Ca(W,Mo)O4: 0.15 mole% is 0.05 wt% Mo, 2 mole% is 0.67 wt%, and 14 mole% is 4.87 wt%. His Fig. 8 powellite–scheelite, about 50 mole% CaMoO4, works out at 19.66 wt% Mo. The pairs agree, so the ladder can be read in either unit.
The quotable line: a yellow glow under shortwave says scheelite with molybdenum, or powellite, but past about 5 wt% Mo it no longer says how much. Modreski confirmed the compositions by semiquantitative energy-dispersive X-ray fluorescence analysis; a lamp in the hand estimates, it does not measure. The powellite sheet records creamy white or yellow to golden yellow under shortwave.
Longwave or shortwave for scheelite?
Shortwave. The sheet names only SW UV; the gem society’s longwave entry is inert or dull yellow, from Sri Lanka; Modreski photographed all his scheelite and powellite figures under shortwave. A longwave-only lamp is therefore the weaker choice: no source read here describes a strong longwave response.
Powellite is the exception in the series. The gem society says powellite fluoresces yellowish to golden yellow under both shortwave and longwave, while its Handbook sheet names shortwave only. The two sources differ on longwave; both are printed in the table. Lamps are compared on the best UV lamp for mineral collecting; that page’s species count is not repeated here.
Scheelite as a detector. The gem society describes gemmologists placing a scheelite behind a shield, a diamond over the hole and shining shortwave through it: Type I diamonds are opaque to shortwave and Type II transparent, so a glowing scheelite indicates Type II. The test depends on scheelite’s shortwave response.
When the answer changes: synthetics, mixed ore and the rest of the family
Synthetic scheelite. The gem society says synthetic or lab-grown scheelite was sold as a diamond lookalike in the 1960s and 70s and may still be offered as natural; that undoped synthetics are colourless; and that colours other than pale green generally fluoresce blue to blue-white under shortwave, some red to orange-red under longwave, and pale green synthetics pink. Documented limit: a blue-white glow is what natural scheelite does and what synthetic scheelite generally does too. It notes curved striae, gas bubbles and rhodium or iridium inclusions in pulled synthetics.
On ore and rock. Modreski says fluorescence has played an important role in the discovery and study of scheelite deposits. A blue-white grain in a pale rock under a shortwave lamp is consistent with scheelite; the sheets of other minerals that glow under shortwave, such as willemite, are the reason it is not proof.
The rest of the family. Stolzite, the lead tungstate, may fluoresce bright red to red-orange under longwave and lemon-yellow under shortwave on its sheet. Wulfenite, ferberite and hübnerite record nothing. Another QUALIFY page in this series, is sodalite UV reactive, deals with a mineral whose sheet names both bands; its lamp-off test is not repeated. The fluorescence guides are in the collecting guides.
Shortwave lamps and exposure: what ICNIRP sets
The specimen is not the exposure question; the lamp is. Table 1 of the ICNIRP 2004 guidelines on limits of exposure to UV radiation gives a spectral weighting of 0.500 at 254 nm against 0.00011 at 365 nm, and marks both as mercury emission lines. The limit arithmetic is worked on is hemimorphite UV reactive and is not repeated. This is not safety advice; read the guideline itself.
On this site. Why minerals glow at all is on fluorescent minerals explained. Nothing on this site is offered for sale; the wanted list is the only commercial route.