Is Hydrozincite Fluorescent?
Hydrozincite fluoresces pale blue to lilac under UV, its Handbook sheet says, naming no band; Modreski (1987) says often bright blue under shortwave UV.
Yes. The Handbook of Mineralogy sheet says hydrozincite, Zn5(CO3)2(OH)6, hardness 2 to 2.5, fluoresces pale blue to lilac under UV, without the word may and without naming a band. Modreski (New Mexico Geology, 1987) adds that it often fluoresces bright blue under shortwave UV and that the cause appears never to have been studied.
In short
- The sheet’s words are the answer. The Handbook of Mineralogy hydrozincite sheet reads: Fluoresces pale blue to lilac under UV. Two colours, no band, and no may: it is stated as a property of the species.
- The two-reference reading. Modreski 1987, New Mexico Geology 9 supplies what the sheet leaves out: hydrozincite often fluoresces bright blue under shortwave UV, photographed on a late crust from the Blanchard mine, New Mexico. Read together: expect blue, look under shortwave first, and do not treat a dark piece as proof of anything, because Modreski says often, not always.
- The qualifier ledger. Over the 7 zinc-suite sheets read for this page, by a ligature-aware script, hydrozincite’s line is the only one with no qualifier. Willemite says typically strongly; smithsonite, hemimorphite, cerussite and calcite say may; aurichalcite records none.
- Documented failure. The colour does not identify it. Smithsonite may fluoresce pale blue and hemimorphite bluish on their own sheets, and all three grow together. Hardness does: 2 to 2.5 for hydrozincite against 4 to 4.5 and 4.5 to 5.
- Cause unknown. Modreski’s caption says the activator is unknown, and this page names none. Lamp exposure limits are in the ICNIRP 2004 guidelines on limits of exposure to ultraviolet radiation; the species facts are on hydrozincite.
| Mineral | Handbook sheet, as printed | Qualifier | Band on the sheet | Modreski 1987, as printed | Band in Modreski | Cause in Modreski |
|---|---|---|---|---|---|---|
| Hydrozincite | Fluoresces pale blue to lilac under UV | None | Not named | Often fluoresces bright blue under shortwave UV; fluorescent blue (Fig. 11) | Shortwave | Never studied; activator unknown |
| Smithsonite | May fluoresce pale green or pale blue under UV | May | Not named | Not normally fluorescent; cadmium-bearing yellow material from the Empire mine fluoresces deep red | Shortwave (deep red); longwave dull orange | - |
| Hemimorphite | May fluoresce bluish under SW UV | May | SW | - | - | - |
| Willemite | Typically strongly fluorescent in yellow-green to yellow-orange under SW and LW UV; may be phosphorescent | Typically strongly | SW and LW | Fluoresces green (Fig. 10) | Shortwave | Mn2+ |
| Cerussite | May fluoresce yellow under LW UV | May | LW | Fluoresces yellow (Fig. 9) | Longwave | Unknown |
| Calcite | May fluoresce red, blue, yellow, and other colors under either SW and LW UV | May | SW and LW | Fluoresces red (Fig. 10) | Shortwave | Mn2+ |
| Aurichalcite | No fluorescence recorded | - | - | - | - | - |
Does hydrozincite glow under UV? What the sheet says
Yes: the sheet says it fluoresces pale blue to lilac under UV, and says it without a qualifier. The line sits in the physical properties of the Handbook of Mineralogy hydrozincite sheet, after hardness 2 to 2.5 and measured density 4.00. It names two colours and no band. It records no phosphorescence; a script search of the sheet for phosph finds nothing.
The qualifier ledger. Method: a script reads the pdftotext text of seven sheets, hydrozincite and the six zinc-suite minerals it names as associates that have cached sheets, and matches any glyph followed by uoresc, case-insensitively, because older sheets set the fl ligature as a stray symbol. The control works: the hemimorphite sheet has no literal fluoresc, yet the search finds its line, may °uoresce bluish under SW UV. Hydrozincite’s line is the only one of the seven without may or typically; aurichalcite’s sheet records no fluorescence at all.
What the ledger does not mean. An unqualified line on a reference sheet is a statement about the species as the editors described it, not a promise about every specimen. The second source qualifies it, below.
Shortwave or longwave? What the second source adds
Modreski names shortwave, and says often rather than always. Modreski 1987, New Mexico Geology 9, a review of mineral fluorescence with New Mexico examples, reads: hydrozincite, Zn5(CO3)2(OH)6, commonly found in small amounts in oxidized zinc ores, often fluoresces bright blue under shortwave UV. His Figure 11 shows a 4 × 3 cm hydrozincite from the Blanchard mine, Socorro Co., a late encrustation on gypsum, captioned fluorescent blue (shortwave UV).
Read together. The two sources agree on blue and differ on two points. The sheet adds lilac and names no band; Modreski names shortwave only and writes often. Neither reports a longwave response, so a longwave lamp alone tests nothing either source states. The lamp choice itself is covered on best UV lamp for mineral collecting.
Not repeated here. The shortwave-first argument and the ICNIRP exposure figures at 254 and 365 nm for the bluish zinc silicate are on is hemimorphite UV reactive; the count of sheets naming no band is on is smithsonite UV reactive. The background to activators and bands is on fluorescent minerals explained.
When a blue glow on a zinc specimen is not hydrozincite
Blue under UV is shared; hardness is not. On their own sheets, smithsonite may fluoresce pale green or pale blue and hemimorphite bluish under shortwave, and the hydrozincite sheet names both as associates. All three can be white crusts on one piece. A glowing crust of hardness 2 to 2.5 fits hydrozincite; smithsonite is 4 to 4.5 and hemimorphite 4.5 to 5.
Documented failure. Modreski calls smithsonite not normally fluorescent and photographs a cadmium-bearing one glowing deep red, while its Handbook sheet says may fluoresce pale green or pale blue: two careful sources describing different specimens. The same caution applies to hydrozincite; the sources describe what they saw, and a given crust may differ.
Other lamps on the same specimen. willemite is the zinc mineral whose sheet says typically strongly fluorescent, under both bands, and cerussite and calcite are on the same associate list. The table above sets out each sheet’s line beside Modreski’s.
Why hydrozincite fluoresces: what is and is not known
Nobody in the sources fetched here knows. Modreski’s text says the cause of this fluorescence appears never to have been studied, and his Figure 11 caption says activator is unknown. Elsewhere in the same paper he explains that most fluorescent minerals depend on activator impurities and that others, quenchers such as Fe2+, Cu2+ or Ni2+, destroy fluorescence; he does not apply that to hydrozincite, and this page does not either.
The copper sibling. aurichalcite is written (Zn,Cu)5(CO3)2(OH)6 on the IMA list, the same proportions as hydrozincite with copper sharing the metal site, and its sheet records no fluorescence. It is tempting to blame the copper. No source fetched for this page says so, so it stays a question, not an answer.
Lamps and eyes. UV exposure limits are set out in the ICNIRP 2004 guidelines on limits of exposure to ultraviolet radiation; this page quotes none and gives no safety advice. The fluorescence pages are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.