Is smithsonite UV reactive
Smithsonite may fluoresce pale green or pale blue, its Handbook sheet says, naming no UV band. It is one of 12 such sheets among 31 fluorescent ones in 176.
Sometimes. The Handbook of Mineralogy says smithsonite, ZnCO3, hardness 4 to 4.5, may fluoresce pale green or pale blue under UV, and it names no band. Of the 176 sheets in this site's mineral reference set, 31 record fluorescence and 12 of those name no band; smithsonite is one. May means some specimens and not others.
In short
- The sheet's wording is the answer: May fluoresce pale green or pale blue under UV. May, not does. Two colours, and no shortwave or longwave. A smithsonite that stays dark under a lamp is not misidentified and not a fake.
- Our count changed, and the reason is worth knowing. Over the 176 sheets now in this site's reference set, 31 record fluorescence and 12 name no band. A literal search for the letters fluoresc over the same 176 finds only 21, because older sheets set fl as a ligature that text extraction turns into a stray symbol. Our earlier figure of 20 of 158 was made the literal way.
- The mineral on the same specimen may be what glows. Smithsonite's own sheet names hemimorphite, willemite, hydrozincite and cerussite among its associates, and all four record fluorescence. Hemimorphite's sheet names shortwave; willemite's names both bands and says typically strongly.
- Magnesite reads almost identically. The magnesite sheet says pale green to pale blue fluorescence and phosphorescence under UV, also with no band. The two carbonates smithsonite forms series with, rhodochrosite and siderite, record none.
- Fluorescence is a poor test for smithsonite. Density does the work: 4.43 against hemimorphite's 3.475, which a kitchen scale and a jug of water can separate.
| Species | Formula | Relation to smithsonite | Fluorescence as recorded | Band named | Hardness |
|---|---|---|---|---|---|
| Smithsonite | ZnCO3 | The species | May fluoresce pale green or pale blue | None | 4 to 4.5 |
| Hemimorphite | Zn4Si2O7(OH)2·H2O | Associate | May fluoresce bluish | Shortwave | 4.5 to 5 |
| Willemite | Zn2SiO4 | Associate | Typically strongly fluorescent, yellow-green to yellow-orange | Shortwave and longwave | 5.5 |
| Hydrozincite | Zn5(CO3)2(OH)6 | Associate | Fluoresces pale blue to lilac | None | 2 to 2.5 |
| Cerussite | PbCO3 | Associate | May fluoresce yellow | Longwave | 3 to 3.5 |
| Anglesite | PbSO4 | Associate | May fluoresce yellow | None | 2.5 to 3 |
| Aurichalcite, malachite, azurite | Copper and zinc carbonates | Associates | Nothing recorded | — | 1 to 2; 3.5 to 4; 3.5 to 4 |
| Magnesite | MgCO3 | Calcite group | May exhibit pale green to pale blue fluorescence and phosphorescence | None | 3.5 to 4.5 |
| Rhodochrosite, siderite | MnCO3, FeCO3 | Series partners | Nothing recorded | — | 3.5 to 4; 3.75 to 4.25 |
Is smithsonite fluorescent? The count, and how it was made
Method. The Handbook of Mineralogy sheets in this site's reference set, all 176 of them, were converted with pdftotext and every sentence containing uoresc was extracted by regular expression, then read. The truncated string is deliberate, and it is the finding.
Result. 31 of the 176 sheets record fluorescence. 19 name a band and 12 do not: anglesite, autunite, baryte, corundum, dolomite, fluorite, hydrozincite, magnesite, meta-autunite, natrolite, smithsonite and sphalerite. Smithsonite's full entry reads May fluoresce pale green or pale blue under UV.
Why the count moved. Searching the same 176 sheets for the full string fluoresc returns 21, not 31. Ten sheets — benitoite, grossular, hemimorphite, marialite, meionite, natrolite, polylithionite, scolecite, uvite and willemite — were typeset with an fl ligature that pdftotext renders as a degree sign, so the word is on the page and invisible to a literal search. This site's published figure of 20 fluorescent sheets in 158, on the fluorite UV page, was made with the literal search and undercounts for that reason. Smithsonite's own status did not change: it was a no-band sheet on the old count and it is one on the new.
So the quotable version is this: smithsonite is one of 12 sheets among 31 fluorescent ones in 176 that record fluorescence without naming a band, and the primary reference will not tell you which lamp to use on it.
When a smithsonite glows, check what else is on the specimen
Smithsonite's sheet lists its associates as hemimorphite, willemite, hydrozincite, cerussite, malachite, azurite, aurichalcite, anglesite. Five of those eight record fluorescence on their own sheets, and three of them name a band where smithsonite does not: hemimorphite may fluoresce bluish under SW UV, cerussite may fluoresce yellow under LW UV, and willemite is typically strongly fluorescent in yellow-green to yellow-orange under SW and LW UV.
That matters because oxidised-zone zinc specimens are frequently mixtures. A pale blue glow on a botryoidal zinc crust could be smithsonite, hydrozincite or hemimorphite, and a lamp alone will not tell you which. Hydrozincite is the soft one at 2 to 2.5; hemimorphite is the light one at 3.475; smithsonite is the heavy one at 4.43.
The two-species version of this problem, with the density test worked through, is on smithsonite vs hemimorphite. Tsumeb is among the localities the smithsonite sheet names; the species itself is on the smithsonite page, and the general mechanism across species is on fluorescent minerals explained.
How to test a smithsonite, and what the lamp costs you
Use both bands. The sheet names neither, so a shortwave-only or longwave-only result is half an answer. A filtered 254 nm lamp and a filtered 365 nm lamp answer different questions.
Test the lamp first on something known, and expect a weak response when there is one: the sheet's colours are pale green and pale blue, which is not the language it uses for willemite. Work in real darkness. The equipment method is the same as for fluorite and is set out on is fluorite UV reactive rather than repeated here.
Eye protection is not optional, particularly under shortwave; the ICNIRP 2004 guidelines set exposure limits across 180 to 400 nm, which covers both collecting bands. The honest economics: two filtered lamps and goggles are a real outlay for a species whose own reference says only that it may glow faintly. If fluorescence is not already your interest, borrow a lamp at a show before buying one for smithsonite. The rest of this section is indexed at the collecting guides. Nothing here is offered for sale; the wanted list sets out what we look for.