Zincite
Zinc oxide (ZnO)
A rare zinc oxide best known for its deep red to orange color, classically from Franklin, New Jersey, and as colorful man-made crystals.
- Mohs hardness
- 4-4.5
- Color
- Deep red, orange-yellow, brownish
- Type
- mineral
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Overview
Zincite is zinc oxide (ZnO), a relatively rare natural mineral crystallizing in the hexagonal system. Its color, ranging from deep blood-red to orange-yellow, comes mainly from manganese impurities; pure synthetic zinc oxide is colorless or white.
Natural zincite is most famously associated with the zinc deposits of Franklin and Sterling Hill, New Jersey, where it occurs with franklinite and willemite in white calcite.
Much of the bright, gem-quality material seen on the market is synthetic, produced as a byproduct of zinc smelting in Poland, yielding spectacular red, orange, green, and yellow crystals.
Formation & geology
Natural zincite forms in metamorphosed zinc ore deposits, most notably at Franklin and Sterling Hill, New Jersey, where ancient zinc-rich sediments were metamorphosed into a unique ore assemblage.
It occurs as massive material, foliated masses, and rare crystals embedded in calcite alongside black franklinite and green willemite. Well-formed natural crystals are extremely rare.
The colorful crystals widely sold to collectors are largely anthropogenic, having grown in the flues and chimneys of zinc smelters in Poland, where vaporized zinc reacted with air to deposit crystalline zinc oxide.
How to identify it
Zincite is recognized by its distinctive deep red to orange-red color, near-adamantine to resinous luster, and an orange-yellow streak that helps distinguish it from many other red minerals. It has a hardness of 4 to 4.5 and perfect cleavage in one direction.
Natural Franklin zincite occurs in white calcite with franklinite and willemite, a diagnostic association. The presence of calcite can be confirmed because it fizzes in dilute acid.
Synthetic smelter zincite is far more transparent and brilliantly colored than natural material and often forms sharp, gemmy crystals, a clue to its man-made origin.
Uses & significance
Zincite is a minor ore of zinc where it occurs in quantity, and zinc oxide itself is hugely important industrially, used in rubber, paints, ceramics, sunscreens, and semiconductors.
For mineral collectors, natural Franklin zincite is a classic and desirable specimen, especially in the company of associated fluorescent minerals. Synthetic zincite is popular for its vivid colors and is occasionally faceted into striking collector gemstones.
In metaphysical circles zincite is associated with energy and creativity, though these claims are not scientifically supported.
Frequently asked questions
Is most zincite on the market natural or synthetic?
Most brightly colored, gemmy zincite crystals sold to collectors are synthetic, grown in Polish zinc smelter flues; natural crystals are very rare.
What gives zincite its red color?
Trace manganese (and iron) impurities produce zincite's red to orange hues; pure zinc oxide is actually colorless or white.
Where does natural zincite come from?
The classic source is the Franklin and Sterling Hill zinc deposits in New Jersey, where it occurs with franklinite and willemite.
Can zincite be made into jewelry?
Transparent synthetic zincite is occasionally faceted, but its softness (Mohs 4 to 4.5) makes it fragile and best suited to collector gems rather than everyday wear.
Zincite guides
In-depth guides for identifying, valuing, and understanding Zincite.
