Is hemimorphite UV reactive?
Sometimes: the Handbook says hemimorphite, a secondary zinc silicate, may fluoresce bluish under shortwave UV. Six of the ten species it grows with do too.
Sometimes. The Handbook of Mineralogy sheet says hemimorphite, hardness 4.5 to 5, may fluoresce bluish under SW UV, and names no longwave response, so a 365 nm lamp alone cannot settle it. Shortwave is also the band with the tighter ICNIRP limit: 60 J/m² at 254 nm for the eye, against 10,000 J/m² across 315 to 400 nm.
In short
- The sheet’s exact words are the answer. The Handbook of Mineralogy hemimorphite sheet reads Strongly pyroelectric; may fluoresce bluish under SW UV. May means some specimens and not others; bluish is the only colour; SW is the only band. A hemimorphite that stays dark is not proven fake.
- The SW-first rule. Because only shortwave is named, test hemimorphite under a 254 nm lamp. A longwave-only result tells you nothing the sheet can confirm. Willemite, whose sheet names both bands and says typically strongly, is the contrast.
- The shortwave limit is far tighter. ICNIRP 2004 gives the unprotected eye 30 J/m² effective, weighted by wavelength. At 254 nm the weighting is 0.500, so the limit is 60 J/m². At 365 nm it is 0.00011, but the 315 to 400 nm total is capped at 10,000 J/m²: about 167 times the 254 nm figure.
- Bluish is not unique. Of the 10 associates the hemimorphite sheet names, 6 record fluorescence. Smithsonite may glow pale green or pale blue, hydrozincite pale blue to lilac, and calcite blue among other colours. Galena, aurichalcite, rosasite and chrysocolla record none.
- Weight decides what the lamp cannot. A 20.00 g piece reads 14.24 g in water as hemimorphite, 15.00 g as hydrozincite and 15.49 g as smithsonite. The full associate list is tabled below, with each sheet’s UV wording as printed.
| Species | Fluorescence as recorded on the sheet | Band named | Hardness | Density | 20.00 g piece in water |
|---|---|---|---|---|---|
| Hemimorphite | May fluoresce bluish | SW | 4.5–5 | 3.475 | 14.24 g |
| Smithsonite | May fluoresce pale green or pale blue | None | 4–4.5 | 4.43 | 15.49 g |
| Hydrozincite | Fluoresces pale blue to lilac | None | 2–2.5 | 4.00 | 15.00 g |
| Calcite | May fluoresce red, blue, yellow and other colours | SW and LW | 3 | 2.7102 | 12.62 g |
| Cerussite | May fluoresce yellow | LW | 3–3.5 | 6.55 | 16.95 g |
| Anglesite | May fluoresce yellow | None | 2.5–3 | 6.38 | 16.87 g |
| Sphalerite | “May be triboluminescent, fluorescent” | None | 3.5–4 | 3.9–4.1 | 14.87–15.12 g |
| Galena | Nothing recorded | — | 2.5–2.75 | 7.58 | 17.36 g |
| Aurichalcite | Nothing recorded | — | 1–2 | 3.96 | 14.95 g |
| Rosasite | Nothing recorded | — | 4.5 | 4.0–4.2 | 15.00–15.24 g |
| Chrysocolla | Nothing recorded | — | ~2–4 | 1.93–2.4 | 9.64–11.67 g |
Does hemimorphite glow under UV light? What the sheet says
Hemimorphite may fluoresce bluish under shortwave UV, and that is all the Handbook records about its response to ultraviolet. The full line on the Handbook of Mineralogy hemimorphite sheet is Strongly pyroelectric; may fluoresce bluish under SW UV. It names no longwave response, no phosphorescence and no cause. This page does not supply one either.
Why a text search can miss it. The sheet was typeset with an fl ligature that pdftotext turns into a stray symbol, so a literal search for fluoresc does not find it. Method used here: the pattern (fl or any single non-letter) followed by uoresc, case-insensitive, line breaks joined. Hemimorphite and willemite are the positive controls and both match; the literal search matches neither.
The rest of the sheet. Hemimorphite is the orthorhombic zinc silicate Zn4Si2O7(OH)2·H2O, hardness 4.5 to 5, density 3.475, colourless or white and pale blue, pale green, grey or brown from impurities. The IMA list writes Zn4(Si2O7)(OH)2·H2O, A, 1962 s.p., Romania. Habit, hemimorphism and localities are on hemimorphite.
Shortwave or longwave for hemimorphite? The SW-first rule
Use shortwave first, because the sheet names no other band. A response under a 254 nm lamp is what the sheet describes; a glow, or none, under 365 nm alone cannot be checked against it. Run the same specimen under longwave afterwards, as a control: a strong longwave glow points to something else on the specimen.
- Bluish under SW, nothing under LW: consistent with hemimorphite, and also with smithsonite, hydrozincite or calcite, whose sheets record blue-range colours. Weigh it.
- Yellow under LW: cerussite’s sheet names exactly that. Anglesite’s says yellow with no band.
- Strong yellow-green under SW and LW: the willemite sheet’s wording, typically strongly fluorescent in yellow-green to yellow-orange. Willemite is not on hemimorphite’s associate list.
- Nothing under either: normal for hemimorphite; the sheet says may.
Weight, not glow, separates the blue-glowing zinc minerals. A 20.00 g piece reads 14.24 g in water as hemimorphite, 15.00 g as hydrozincite and 15.49 g as smithsonite. The two-species test is worked on smithsonite vs hemimorphite.
Is shortwave UV more hazardous? The ICNIRP numbers at 254 and 365 nm
Per joule, ICNIRP weights 254 nm about 4,500 times more heavily than 365 nm; for the eye the gap in the limits is about 167 times. The ICNIRP 2004 guidelines on limits of exposure to UV radiation set 30 J/m² effective, spectrally weighted, for the unprotected eye and skin in an 8-hour period, and cap the eye’s unweighted total from 315 to 400 nm at 10,000 J/m². Table 1 marks 254 and 365 nm as mercury lines.
- 254 nm: weighting S = 0.500, so the limit is 30 ÷ 0.500 = 60 J/m².
- 365 nm: S = 0.00011, so the weighted figure is 2.7 × 105 J/m². For the eye the 10,000 J/m² UVA cap is lower and governs.
- Ratios: 0.500 ÷ 0.00011 = 4,545 on the weighting; 10,000 ÷ 60 = 167 on the eye limits.
What the numbers do not tell you. ICNIRP gives the permissible time as 30 J/m² divided by the effective irradiance, which depends on the lamp, its filter and the distance. We have measured no lamp and give no times. This is not safety advice; read the guideline itself. Lamps are compared on the best UV lamp for mineral collecting.
When a bluish glow on a zinc specimen is not hemimorphite
Six of the ten minerals the hemimorphite sheet lists as associates also record fluorescence, and three of them in blue-range colours. The sheet’s association line names smithsonite, sphalerite, galena, cerussite, anglesite, calcite, aurichalcite, rosasite, hydrozincite and chrysocolla. Read the same ligature-aware way, smithsonite, hydrozincite, calcite, cerussite, anglesite and sphalerite record fluorescence; galena, aurichalcite, rosasite and chrysocolla record none.
Only hemimorphite names shortwave alone. Calcite’s sheet names both bands, cerussite’s names longwave, and the other three that fluoresce name no band. So an SW-only bluish response is the one most specific to hemimorphite among these eleven sheets, but it is not proof. The smithsonite side of this problem is set out on is smithsonite UV reactive and is not repeated.
Mixed crusts are the usual case. Hemimorphite is a secondary mineral of the oxidised zone of zinc deposits, per its sheet, which lists ten associates, so one crust may hold more than one of these species: weigh or test the part that glows. Why some minerals fluoresce at all is on fluorescent minerals explained, and the other guides are in the collecting guides. Nothing here is offered for sale; the wanted list is the only commercial route.