Properties
| Chemical formula | Zn₂SiO₄ |
|---|---|
| Elements | Zn, Si, O |
| Crystal system | Trigonal |
| Mohs hardness | 5.5 |
| Density | 4.246 g/cm³ |
| Streak | — |
| Color | — |
| IMA symbol | Wlm |
| Nickel–Strunz class | 9.AA.05 |
“—” means no reliable value in Wikidata yet. Check Mindat for full data.
✺ Glows under UV
| Longwave UV (~365 nm) | Green (usually weaker) |
|---|---|
| Midwave UV (~310 nm) | Green |
| Shortwave UV (~254 nm) | Bright yellowish green |
| Phosphorescence (afterglow) | Occasionally a vivid green afterglow |
Willemite is the green star of Franklin and Sterling Hill, New Jersey, where it glows alongside red calcite. Man-made willemite was used as an early fluorescent-tube phosphor.
Reactions vary by locality and specimen; many specimens of a fluorescent species do not glow. Shortwave UV can burn skin and damage eyes. Wear UV-blocking glasses, and never look into any UV lamp. Sources: Franklin Mineral Museum fluorescent mineral checklist · Wikipedia: Willemite. More UV-reactive stones →
🌍 Where it's found
Type locality (where it was first described): Kelmis, Belgium
- Type locality
- Notable source / deposit
- Country of origin
Marker positions are approximate (region or locality level). Type localities from Wikidata; notable sources curated by Crystopedia.
Learn more
- Willemite on Mindat.org
- Wikipedia article
- Wikidata item Q409139 (source of this page's data – you can correct it there)
IMA mineral species
5–6
Trigonal
RedYellowGreenBluePinkBrownBlackGrayWhite & Clear
LongwaveMidwaveShortwavePhosphorescentUV reactive