Is mimetite UV reactive?
Sometimes: mimetite may fluoresce reddish yellow under LW or SW UV, its Handbook sheet says. Of the three Pb5(XO4)3Cl minerals, vanadinite records no glow.
Sometimes. The Handbook of Mineralogy sheet says mimetite, a lead arsenate of hardness 3.5 to 4, may fluoresce reddish yellow under LW or SW UV. May means some specimens; or means either lamp can show it, so a dark result under one lamp proves nothing. Pyromorphite records the same bands; vanadinite records no fluorescence.
In short
- The sheet’s exact words. The Handbook of Mineralogy mimetite sheet reads Piezoelectric; may fluoresce reddish yellow under LW or SW UV. May: some specimens and not others. Reddish yellow: the only colour. LW or SW: both bands are named.
- The either-lamp rule. Because the sheet joins the bands with or, test under both a 365 nm and a 254 nm lamp before calling a mimetite unreactive. A specimen dark under one lamp has not been tested against the sheet until it has seen the other.
- The three-apatite lamp key. A script over the IMA-CNMNC Master List finds three rows written Pb5(XO4)3Cl: mimetite, pyromorphite and vanadinite. Pyromorphite’s sheet: may fluoresce yellow to orange under LW and SW UV. Vanadinite’s records none. A glow points away from vanadinite; it cannot choose between mimetite and pyromorphite.
- Weight does not rescue it. A 20.00 g piece reads 17.24 g in water as mimetite, 17.16 g as pyromorphite and 17.09 g as vanadinite: 0.15 g across all three. The two-species problem is set out on how to tell pyromorphite from mimetite and is not repeated.
- Lead and arsenic. Worked from the formula, mimetite is 69.61% lead and 15.10% arsenic by mass. Toxicity is covered on toxic minerals in a collection; this page is not advice.
| Species | Formula (IMA) | Fluorescence as recorded on the sheet | Bands named | Hardness | Density | 20.00 g piece in water |
|---|---|---|---|---|---|---|
| Mimetite | Pb5(AsO4)3Cl | May fluoresce reddish yellow | LW or SW | 3.5–4 | 7.24 | 17.24 g |
| Pyromorphite | Pb5(PO4)3Cl | May fluoresce yellow to orange | LW and SW | 3.5–4 | 7.04 | 17.16 g |
| Vanadinite | Pb5(VO4)3Cl | Nothing recorded | — | 2.5–3 | 6.88 | 17.09 g |
| Wulfenite | Pb(MoO4) | Nothing recorded | — | 2.75–3 | 6.5–7.5 | 16.92–17.33 g |
| Cerussite | Pb(CO3) | May fluoresce yellow | LW | 3–3.5 | 6.55 | 16.95 g |
| Anglesite | Pb(SO4) | May fluoresce yellow | None named | 2.5–3 | 6.38 | 16.87 g |
| Smithsonite | Zn(CO3) | May fluoresce pale green or pale blue | None named | 4–4.5 | 4.43 | 15.49 g |
| Willemite | Zn2(SiO4) | Typically strongly fluorescent, yellow-green to yellow-orange | SW and LW | 5.5 | 3.89–4.19 | 14.86–15.23 g |
Does mimetite glow under UV light? What the sheet says
Mimetite may fluoresce reddish yellow under longwave or shortwave UV, and that is all its Handbook sheet records about ultraviolet. The full line on the Handbook of Mineralogy mimetite sheet is Piezoelectric; may fluoresce reddish yellow under LW or SW UV. It records no phosphorescence and gives no cause, and this page supplies none.
How it was read. Unlike the benitoite, hemimorphite and willemite sheets, the mimetite sheet prints fluoresce as plain text, so a literal search finds it. The method was still ligature-aware, (fl or any single non-letter) followed by uoresc, case-insensitive, in the Physical Properties field, with hemimorphite, willemite and benitoite as positive controls; all match. Of the eight sheets in the table above, six record fluorescence.
The rest of the sheet. Mimetite is hexagonal, Pb5(AsO4)3Cl, in the apatite group, hardness 3.5 to 4, density 7.24, pale to bright yellow, yellowish brown, yellow-orange, white or colourless, with a white streak and resinous to subadamantine lustre. Its name is from the Greek for an imitator, as it imitates pyromorphite. Habit, the clinomimetite dimorph and localities are on mimetite.
Longwave or shortwave for mimetite? The either-lamp rule
Use both, because the sheet names both and joins them with or. That wording differs from the hemimorphite sheet, which names shortwave alone, and from cerussite’s, which names longwave alone. Under the mimetite sheet a response under either lamp is consistent, and a blank under one is not a result.
- Longwave first, 365 nm. If reddish yellow appears, it is consistent with the sheet; note it and still check shortwave.
- Then shortwave, 254 nm. A reddish-yellow glow here alone is equally consistent.
- Dark under both: normal. The sheet says may; a non-glowing mimetite is not shown to be anything else.
- Green or blue: not the mimetite wording. On a zinc-bearing specimen, smithsonite’s sheet records pale green or pale blue and willemite’s yellow-green; check what on the matrix is glowing.
Mixed specimens. The sheet’s association line names cerussite, anglesite, smithsonite, willemite, pyromorphite and wulfenite, and five of those six sheets record fluorescence, so a glow on a matrix piece may not be the mimetite. How a related arsenate behaves in measured tests is on is adamite UV reactive.
Can UV tell mimetite from pyromorphite and vanadinite? The three-apatite lamp key
Method and count. Every line of the September 2026 IMA-CNMNC Master List, saved as text with pdftotext -layout, was parsed by script (controls: the mimetite, pyromorphite, vanadinite and benitoite rows must parse with their known formulae). Three rows are written Pb5(XO4)3Cl: mimetite (As, G, 1832, Germany), pyromorphite (P, G, 1813, Germany) and vanadinite (V, G, 1838, Mexico).
The key. Mimetite: may fluoresce reddish yellow under LW or SW. Pyromorphite: may fluoresce yellow to orange under LW and SW. Vanadinite: nothing recorded. So a yellow-to-orange glow points away from vanadinite but leaves mimetite and pyromorphite both open, because the colours and bands overlap. Documented negative: the lamp cannot settle the commonest mimetite question, and neither can the scale, at 17.24 against 17.16 g in water for a 20.00 g piece.
What does help with vanadinite. Hardness: vanadinite 2.5 to 3 on its sheet, mimetite and pyromorphite 3.5 to 4; testing it properly is on how to test mineral hardness properly. The mimetite–pyromorphite series itself is on pyromorphite and vanadinite has its own page.
How much arsenic is in mimetite? The Phoenixville analysis, worked
From the formula. Pb5(AsO4)3Cl, on standard atomic weights, is 69.61% lead, 15.10% arsenic and 2.38% chlorine by mass. The sheet’s theoretical column, PbO 74.99 and As2O5 23.17, gives the same: 69.61% lead and 15.11% arsenic, the second decimal a rounding of the oxide figure.
From the analysis. The sheet’s one analysis, from Phoenixville, Pennsylvania, carries As2O5 23.17, PbO 74.58 and P2O5 0.14. Worked, that is 69.23% lead and 15.11% arsenic, with arsenic to phosphorus about 102 to 1 by atoms: an arsenate end of the series, not an intermediate. A sample from a mixed locality would need its own analysis; colour and glow do not supply one.
What to do with that. Nothing here is health or handling advice. Lead and arsenic minerals are covered on toxic minerals in a collection. UV exposure limits are in the ICNIRP 2004 guidelines, linked below. Why some minerals fluoresce at all is on fluorescent minerals explained, and the other guides are in the collecting guides. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.