Zincite
Zincite, ZnO: hexagonal zinc oxide, hardness 4, density 5.66, 80.34% zinc, red-orange with a yellow-orange streak; New Jersey ore, and the Polish by-product.
Zincite is zinc oxide, ZnO on the September 2026 IMA list: hexagonal, hardness 4, density 5.66, yellow-orange to deep red with a yellow-orange streak, and 80.34% zinc by mass. Its Handbook sheet names Franklin and Sterling Hill, New Jersey, first. The bright transparent crystals sold as “Polish zincite” are a by-product of zinc oxide kilns, per Gems & Gemology.
In short
- The species. The September 2026 IMA-CNMNC Master List lists zincite as ZnO, status G, 1845, USA. The Handbook of Mineralogy sheet writes (Zn,Mn2+)O: hexagonal, crystals rare and pyramidal to 2.5 cm, usually massive or foliated; cleavage {10-10} perfect; hardness 4; density 5.66; yellow-orange to deep red; streak yellow-orange. A 20.00 g piece reads 16.47 g in water.
- New Jersey, on the sheet. Distribution opens “In the USA, from Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey”, and both printed analyses are from Sterling Hill, where the sheet calls it a primary mineral of metamorphosed stratiform zinc orebodies, associated with franklinite, willemite and calcite. The district is on Franklin and Sterling Hill.
- Polish zincite is not a mineral find. Zhang, Gao and Shi (2017), Gems & Gemology describe gem-quality synthetic zincite from Poland as “an industrial by-product of zinc oxide processing”, grown in the chimney vents of kilns at a Lower Silesia foundry and on the market since the early 1980s. Their 10 samples measured SG 5.66 to 5.70, the same as the sheet’s 5.66.
- The manganese line. Recast by script, the two Sterling Hill analyses hold 0.0031 and 0.0033 Mn per ZnO unit (MnO 0.27 and 0.29 wt%). GIA’s ICP-MS found 1.53 to 7.55 ppm Mn in the Polish crystals, which they say is “dramatically lower” than in natural zincite. Density cannot separate the two; manganese, measured in a laboratory, can.
- Under UV. The sheet: “Rare pale yellow fluorescence under LW UV.” The FMS database lists 5 zincite records, all from Sterling Hill, all yellow under longwave and none with a shortwave line. Lamp exposure limits are in the ICNIRP 2004 guidelines on ultraviolet exposure; this page is not safety advice.
| Quantity | Sterling Hill analysis (1) | Sterling Hill analysis (2), microprobe | Polish by-product (GIA, 10 samples) |
|---|---|---|---|
| ZnO, wt% | 99.63 | 98.88 | “almost pure zinc and oxygen” by XRF |
| MnO, wt% | 0.27 | 0.29 | Mn 1.53–7.55 ppm by ICP-MS, mean 3.38 |
| Mn per ZnO unit, worked | 0.0031 | 0.0033 | 0.0000023–0.0000112 |
| FeO, wt% / Fe | 0.01 | 0.23 | Fe 38.31–104.92 ppm |
| Density | 5.66 measured; 5.6730 calculated; 5.675 from the cell, worked | — | SG 5.66 to 5.70, hydrostatic |
| 20.00 g piece in water | 16.47 g | — | 16.47 to 16.49 g |
| Habit | Crystals rare, pyramidal, to 2.5 cm; usually massive or foliated | — | Hexagonal prisms and pyramids, contact twins on (0001); transparent |
| Colour; lustre | Yellow-orange to deep red; subadamantine to resinous | — | Reddish orange to yellow to greenish yellow; subadamantine to vitreous |
| Origin | Primary mineral in metamorphosed zinc orebodies, New Jersey (sheet) | — | Grown in chimney vents of zinc oxide kilns, Lower Silesia |
What is zincite? The zinc oxide
Zincite is ZnO on the September 2026 IMA list, status G (grandfathered), 1845, with the USA as the country of first description; the first reference is the Handbuch der Bestimmenden Mineralogie (Braumüller and Seidel, Wien, 1845) and the second Canadian Mineralogist 23 (1985), 647. A script over the list finds one row whose formula is built of zinc and oxygen alone, and it is zincite. The Handbook of Mineralogy zincite sheet writes (Zn,Mn2+)O, the IMA list ZnO. Worked on standard atomic weights the formula mass is 81.38: 80.34% zinc, 19.66% oxygen. That 80.34% is the figure on is smithsonite a carbonate, where zincite stands as the oxide beside the carbonate and the silicates.
What the sheet records. Hexagonal, point group 6mm, space group P63mc (synthetic), a = 3.24992, c = 5.20658 Å, Z = 2. Crystals are rare, typically pyramidal and hemimorphic with a large {0001}, to 2.5 cm, rarely curved; more often it is in broad cleavages, foliated, granular, compact or massive. Twinning on {0001}. Cleavage {10-10} perfect, with a parting on {0001} commonly distinct; fracture conchoidal; brittle; hardness 4. Density 5.66 measured and 5.6730 calculated; the cell, worked, gives 5.675. Uniaxial (+), ω 2.013, ε 2.029.
Colour and streak. Yellow-orange to deep red, rarely yellow, green or colourless; deep red to yellow in transmitted light; streak yellow-orange; lustre subadamantine to resinous. The sheet’s reference list includes Dunn (1979), “Light green zincite from Sterling Hill”. The streak technique is on how to use a streak plate.
Where is zincite found? Franklin and Sterling Hill first
Distribution, as printed. “In the USA, from Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey; in the Tonopah-Belmont mine, Osborne district, Maricopa Co., Arizona, the result of a mine fire; in volcanic ash from Mt. St. Helens, Skamania Co., Washington. At Tsumeb, Namibia. From Kipushi, 28 km southwest of Lubumbashi, Katanga Province, Congo.” It adds: “Other localities have been reported but lack supporting data or an accurate location.” Tsumeb has its own page.
Three ways to form, per the sheet. “A primary mineral in metamorphosed stratiform zinc orebodies (New Jersey, USA); a secondary mineral altered from other zinc minerals in oxidized zinc-rich ore deposits; a product of volcanism.” The associates are franklinite, willemite and calcite in New Jersey, and zinc, sphalerite, smithsonite, hemimorphite and hausmannite elsewhere. Both chemical analyses on the sheet are from Sterling Hill.
No type locality claimed. The sheet marks none and the IMA list gives only the country, USA; see what is a type locality. The New Jersey district, its ore and its fluorescent minerals are covered on Franklin and Sterling Hill, which this page does not repeat.
Is Polish zincite real? The kiln by-product
It is real zinc oxide, but not a mineral find. Zhang, Gao and Shi (2017), Gems & Gemology write that “Gem-quality synthetic zincite from Poland, an industrial by-product of zinc oxide processing, has been available in the market since the early 1980s.” They say it “emerged from an unnamed foundry in Poland’s Lower Silesia Province” and grew “in the chimney vents of industrial kilns producing zinc oxide powder, through a process similar to chemical vapor deposition”, and that it was sold from the early 1980s until the 2000s and now comes only from existing stocks. They call it by-product zincite, and so does this page.
The manganese line, worked. GIA measured manganese at 1.53 to 7.55 ppm (mean 3.38) in five samples, “dramatically lower than Mn contents in natural material”. The sheet’s two Sterling Hill analyses carry MnO 0.27 and 0.29 wt%; recast on standard atomic weights that is 0.0031 and 0.0033 manganese atoms per ZnO unit, which is why the sheet writes (Zn,Mn2+)O. Worked the same way, GIA’s 1.53 to 7.55 ppm is 0.0000023 to 0.0000112 manganese per unit, roughly 280 to 1,400 times less.
Documented failure: weight does not tell them apart. GIA’s samples gave SG 5.66 to 5.70; the sheet gives 5.66. A 20.00 g piece reads 16.47 g in water either way, on the method at how to measure specific gravity at home. GIA separated them by ICP-MS, by Raman peaks they found in the by-product spectra and not in the natural ones (near 379, 410, 540, 580, 660 and 1150 cm−1) and by oval “tadpole-like” inclusions of carbon-bearing material, “possibly belonging to soot and/or gases”. Transparency and colour are hints, not proof; the sheet records natural zincite as transparent in thin fragments. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.
Does zincite fluoresce?
Rarely, and under longwave, on the sheet. The physical-properties line reads “Rare pale yellow fluorescence under LW UV.” The word is rare: the sheet does not say zincite typically fluoresces. By contrast the willemite sheet says “Typically strongly fluorescent”.
What the FMS database holds. The FMS Fluorescent Mineral Database zincite list, fetched 14 November 2026, links 5 specimen records. A script read each record’s summary of luminescence responses: all 5 are from Sterling Hill, all 5 record zincite as yellow under longwave, one also yellow under midwave, and none records a shortwave response or an afterglow. That is a gallery of specimens chosen because they glow, so it says what fluorescent zincite does, not how often zincite fluoresces.
Lamps. UV exposure is covered by the ICNIRP 2004 guidelines on ultraviolet exposure; the lamp background is on fluorescent minerals explained. This is a routing line, not safety advice. Other zinc minerals are in the species index.