Is celestite UV reactive?
Often. The Handbook sheet for celestine (celestite), SrSO4, prints no fluorescence, but all 16 Fluorescent Mineral Society records glow white or blue under UV.
Often, but not on its sheet. The Handbook of Mineralogy sheet for celestine, the IMA name for celestite, SrSO4, hardness 3 to 3.5, prints no fluorescence. The Fluorescent Mineral Society’s database holds 16 celestine records, and every one glows white or blue: 13 under longwave, 12 under shortwave, 8 with an afterglow. Neighbouring calcite can glow identically.
In short
- The sheet is silent. The Handbook of Mineralogy celestine sheet prints no luminescence of any kind. A ligature-aware script finds the lines on hemimorphite and willemite (the positive controls) and on baryte, strontianite, calcite, fluorite and dolomite, and nothing on celestine, anhydrite or gypsum. Modreski (1987), New Mexico Geology 9 does not mention celestine either.
- The record ledger. The Fluorescent Mineral Society’s Fluorescent Mineral Database links 16 specimen records from its celestine page. Every celestine entry gives white or blue fluorescence: under longwave in 13 records, shortwave in 12, midwave in 1. Eight summary fields log an afterglow, green on every one after longwave; the descriptions of three more mention one. These are specimens chosen because they glow, so they show that celestine can respond, not how often it does.
- Documented failure: the glow next door. On two Lime City, Ohio, records the calcite on the same piece is logged with exactly the celestine’s responses, on one of them strontianite too, and on a Maybee, Michigan, record the contributor found that the apparent glow of the sulphur was light from the calcite and celestine around it. A colour under the lamp does not say which mineral is glowing.
- Confirm the spot, not the glow. Calcite and celestine overlap in hardness, 3 against 3 to 3.5, so the test is cleavage and weight: a 20.00 g single crystal reads 14.96 g in water as celestine and 12.62 g as calcite. The full sequence is on how to identify celestite; the species facts are on celestine.
- Lamps. Exposure limits for 180 to 400 nm are in the ICNIRP 2004 guidelines on limits of exposure to ultraviolet radiation. Other hazards are routed to toxic minerals in a collection. This page is not safety advice.
| Locality in the records | Records | Celestine fluorescence recorded | Afterglow recorded | Other minerals logged as glowing on the same records | On the Handbook sheet’s Distribution? |
|---|---|---|---|---|---|
| Sicily, Italy (La Grasta mine, Serradifalco, Caltanissetta, Agrigento) | 6 | White on 5, blue on 1; longwave on 4, shortwave on 5 | 2 of 6: green after longwave; blue after shortwave | Aragonite on 3: pink under longwave where the celestine is white | Yes: Girgenti, Caltanissetta, and elsewhere in Sicily |
| Stoneco Lime City Quarry, Ohio, USA | 6 | White on 3, blue on 3; longwave on 6, shortwave on 5, midwave on 1 | 4 of 6: green after longwave; white, blue or green after shortwave | Calcite logged identically on 2 and described alike on 1; strontianite logged identically on 1 | No |
| Clay Center, Ohio, USA | 2 | Blue; longwave on 1, shortwave on 1 | None logged | Fluorite on both, white | Yes: Clay Center, Ottawa Co. |
| Maybee, Michigan, USA (a sulphur record) | 1 | White, longwave and shortwave | Green after longwave; blue after shortwave | Calcite, logged identically; sulphur logged green, traced by the contributor to transmitted light | Yes: the Scofield quarry, Maybee |
| Machów mine, Poland | 1 | White, longwave | Green after longwave | None logged | No |
| All 16 records | 16 | White or blue only; longwave 13, shortwave 12 | 8 of 16 (11 with descriptions) | — | Sheet itself prints no fluorescence |
Does celestite glow under UV light?
Celestite can glow, and every specimen record read for this page does; its reference sheet does not record it. Celestine, Sr(SO4) on the September 2026 IMA list (celestite is the common form of the name), has a Handbook sheet that prints cleavage, hardness 3 to 3.5, density 3.97, optics and colour, and no luminescence line at all. Silence on a sheet is not a statement that a mineral never glows; it means the sheet does not record it as a property of the species.
Method. The search reads the pdftotext text of each sheet up to its reference list and matches uoresc (so a dropped or garbled fl ligature still matches), phosphoresc, luminesc and UV, case-insensitively. It finds the lines on hemimorphite and willemite, the positive controls. Among celestine’s look-alikes and neighbours it finds baryte (may fluoresce and phosphoresce cream to spectral colors under UV), strontianite (fluorescent under UV), calcite, aragonite, fluorite and dolomite, and on celestine, anhydrite, gypsum and sulphur nothing.
A different effect that is recorded. Bernstein (1979), American Mineralogist 64, 160–168 notes weak thermoluminescence of celestite reported in the older literature, and a study giving two thermoluminescence peaks, at 80 to 100 °C and 180 to 240 °C. That is light on heating, not under a UV lamp, and this page draws nothing about UV from it.
What colour does celestite fluoresce? The record ledger
White or blue, in every record read here. The Fluorescent Mineral Society’s database links 16 specimen records from its celestine page. A script read the luminescence summary of each saved page. Every celestine entry is white or blue: white on 5 of the 6 Sicilian records and at Machów and Maybee, blue on both Clay Center records, and three of each at Lime City. Longwave fluorescence is logged on 13 records, shortwave on 12 and midwave on 1. The lamps named are a 365 nm LED for longwave and a 254 nm mercury lamp or 255 nm LED for shortwave.
Afterglow. Eight records log an afterglow in their summary fields. After longwave it is green on every one of them; after shortwave it is blue, white or green. The descriptions of three more, from Agrigento and Lime City, mention a celestine afterglow, one of them a very long-lasting one, which brings the count to 11 of 16. Afterglow colour, like fluorescence colour, is reported per specimen.
The limit of the ledger. A database of fluorescent specimens collects pieces that glow. It cannot say what share of celestine does not, and none of the 16 records is a non-response. A band missing from a record may simply not have been tried. Lime City and Machów are not on the Handbook’s locality list, which the sheet says is limited to a few localities for fine and large crystals.
Is it the celestite or the calcite glowing?
On a mixed specimen, the records say you cannot tell from the colour. On three Lime City records, a celestine, strontianite and calcite cluster, a two-sided celestine and calcite piece and celestine and calcite on limestone, the calcite is logged or described with the same or a similar blue-white fluorescence and phosphorescence as the celestine. On three Sicilian records aragonite is logged too, but pink under longwave where the celestine is white, so there the colour does separate them. On the Maybee sulphur record the contributor tested a matrix-free fragment of the sulphur, found it not fluorescent, and concluded that its apparent glow was light emitted by the calcite and celestine beneath it.
So confirm the spot. Hardness does not help here: calcite is 3 and celestine 3 to 3.5. Cleavage and weight do. Celestine cleaves perfectly on {001}; calcite on {10-11} into rhombs. A 20.00 g single crystal reads 14.96 g in water as celestine and 12.62 g as calcite, on the method at how to measure specific gravity at home. Baryte, its series partner, may fluoresce on its own sheet and reads 15.56 g. The other checks are on how to identify celestite, and why calcite glows is on is calcite UV reactive.
Why the page names no cause. Three records attribute the glow to organic matter, one of them as likely, from their emission spectra. No source fetched for this page measured an activator in celestine, so this page makes no activator claim. The same caution applies on is sphalerite UV reactive.
Which UV lamp, and is it safe?
Both bands appear in the records. Nine records log a response under both longwave and shortwave, four under longwave only and three under shortwave only, so the ledger does not favour one band. Choosing a lamp is on best UV lamp for mineral collecting and the background on fluorescent minerals explained.
Safety is not covered here. Exposure limits for ultraviolet radiation from 180 to 400 nm are set out in the ICNIRP 2004 guidelines on limits of exposure to ultraviolet radiation. Anything else hazard-related is on toxic minerals in a collection. This page is not safety advice. Whether celestite breaks easily is answered on is celestite fragile, and the quartz question on is celestite a quartz. More 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.