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 compact botryoidal travertine calcite specimen from New York, showing the smooth, rounded, grape-like clusters that give botryoidal calcite its distinctive appearance. Calcite forms through the rapid precipitation of calcium carbonate from mineral-rich groundwater, often around spring outlets or in cave systems, where dissolved calcite is deposited layer upon layer as the water evaporates or degasses carbon dioxide. Rather than growing as sharp, faceted crystals, this rapid formation process produces the smooth, bulbous surface seen here, sometimes described as having a soft, almost organic texture. The warm tan and cream banding visible across the piece reflects subtle mineral impurities and changes in the water chemistry during each stage of deposition, essentially recording a timeline of the spring’s activity. Calcite has been used historically as a building and ornamental stone for exactly this reason — the banding creates a natural, attractive pattern when cut and polished. This raw, uncut piece preserves the natural botryoidal surface texture for collectors who want to see calcite in its original formation habit rather than as a finished slab.
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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