Specimen at a glance
| Mineral | Calcite |
|---|---|
| Chemistry | CaCO3 |
| Mohs hardness | 3 |
| Crystal system | Trigonal |
| Locality | Ohio |
| Form | Crystal point |
| You receive | The exact specimen pictured |
About this specimen
Calcite is calcium carbonate (CaCO₃), one of the most common minerals on Earth, but also one of the most varied — it’s documented in well over 800 distinct crystal shapes, more than any other mineral, from flat plates to sharp points like this one. This piece’s warm honey-gold color comes from trace iron impurities picked up as it crystallized in Ohio’s dolomite quarries, a region known among collectors for producing clear, sharply formed calcite.
At Mohs hardness 3, calcite is soft enough to scratch with a knife or even a copper coin, so it should be handled more carefully than quartz — keep it away from harder stones in storage and clean with just a soft, dry cloth. Calcite also reacts visibly with acid (a drop of vinegar will fizz on it), a classic identification test if you’re ever unsure whether a mineral is calcite.
Approximately 1.5″ tall with a sharp natural termination and warm golden color throughout, it’s an affordable, well-formed piece for a starter collection or a calcite specialist.
Inside the Calcite
One of the most common minerals on Earth — and one of the only ones you can prove is calcite with nothing but a coin and a drop of vinegar.
The story: Calcite crystallizes out of calcium-rich water almost anywhere conditions allow — caves, hydrothermal veins, sedimentary pockets — which is why it shows up in more shapes than almost any other mineral: sharp dogtooth points, flat nailhead rhombs, honey-gold masses, even the travertine that lines old hot springs. Every one of those forms is chemically the same mineral, just grown under different conditions.
Why collectors chase it: Calcite is the classic demonstration of birefringence — a clear piece laid over printed text splits the letters into a visible double image, a party trick that only a handful of minerals can do. Add in the sheer range of natural color and habit (the golden-toned Ohio pieces get their warmth from iron staining) and it’s an easy mineral to build a whole sub-collection around.
Care: This is the one to handle more carefully than most of the shop: at Mohs 3 it scratches under a fingernail-plus-effort, it splits cleanly along three flat planes if dropped (perfect rhombohedral cleavage), and it will visibly fizz on contact with vinegar or other mild acids — keep it away from acidic cleaners and store it apart from harder stones that could scratch 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 Ohio. 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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