Specimen at a glance
| Mineral | Calcite |
|---|---|
| Chemistry | CaCO3 |
| Mohs hardness | 3 |
| Crystal system | Trigonal |
| Locality | New York |
| You receive | The exact specimen pictured |
About this specimen
A single calcite crystal from New York State, labelled to the state by the collection it came out of. The crystal is a stout, barrel-shaped form with its steep faces stepped and finely striated in parallel lines — calcite’s normal way of recording pauses in its own growth. Colour runs from pale straw to a smoky honey-gold depending on which face is turned to the light, and the crystal is translucent rather than fully transparent.
What makes this one worth keeping is the dark bladed crystals lying across one face and along the base: near-black, elongated and splintery, with a grey-green metallic sheen where they catch the light. They sit set into the calcite rather than resting on it, which means they were already in place when the calcite grew around them. A patch of pale grey matrix is still attached at the base.
Calcite is calcium carbonate, Mohs 3, with perfect rhombohedral cleavage in three directions. That makes it soft and knock-sensitive — it will scratch against harder stones in a drawer and can cleave cleanly if dropped. Keep it on display rather than stored loose, dust it dry, and never put calcite in vinegar or any acidic cleaner; it etches on contact.
New York is classic calcite country and has produced fine crystals from several districts. The label with this specimen records the state rather than a specific quarry, so the state is all we claim for it.
Calcite: the science
- Calcite has perfect rhombohedral cleavage: tap it hard and it breaks into slanted blocks along three directions.
- Clear calcite shows double refraction. Set it on printed text and you see the letters twice.
- It fizzes in weak acid, a classic field test. That is also why acid cleaners will damage it.
Go deeper
Want the full story on calcite: how it forms, how to identify it, and what makes a great specimen?
Questions about this piece
What is calcite?
Calcite is calcium carbonate, the mineral that makes up limestone, marble, cave formations, and many seashells. It crystallizes in more shapes than almost any other mineral.
Where was it found?
This piece comes from New York. We list a locality whenever it is known, because where a mineral formed is part of its story and its value.
How hard is it, and how should I care for it?
It rates 3 on the Mohs scale. Calcite is soft (Mohs 3) and cleaves easily. Handle gently, never use vinegar or acid cleaners, and dust with a soft brush. Rinse only briefly in plain water.
Is this the exact piece I will receive?
Yes. This listing was photographed individually, and you receive the exact piece shown in the photos.
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