Miners also call calcite calcspar.

Calcite consists of the elements
calcium, carbon and oxygen.

The chemical formula is CaCO₃.

The crystals of calcite look colourless.
However, this rarely occurs in nature.
Tiny quantities of other elements colour the crystals
in all the colours of the rainbow: white, grey, yellow,
pink, red, blue, green, brown and even black.

Calcites can form hundreds of different crystal shapes. 
They are true shape magicians.

Double spar is particularly impressive. 
It is transparent, clear and has the shape of a rhombohedron. 
If you look through it, you can see everything twice!

The scalenohedron is also a special crystal shape 
that is somewhat reminiscent of a  jelly bag cap.

On the Mohs hardness scale, calcite has a hardness of 3.
This means that it is a little harder
than your fingernail.
So you can't scratch it.

On the Mohs scale of hardness, diamond
is the hardest mineral in the world with a hardness of 10.
Tallow, on the other hand, is very soft and has a hardness of 1.

If you hit a piece of calcite with a hammer,
straight and smooth cleavage pieces are produced.
This is a typical sign of good cleavage.
Sometimes you can recognise such fissures in the crystal.
They look like cracks in the glass. In mineralogy, this good cleavage is described as "perfect."

Calcite is a continuous mineral.
This means that it is very common and
occurs all over the world.

You will often find it together with the minerals
Quartz, fluorite (fluorspar), barite (barite),
galena (galena), sphalerite (zinc blende)
or pyrite (fool's gold).

Calcite is also a component of rocks such as marble or limestone.

Calcite is a very important raw material because
it is needed in the production of gypsum and cement.

Fertilisers can also be made from calcite.

The effect of birefringence
is particularly important for lenses.
This can be used to build polarisation microscopes 
in order to examine the composition of rocks even more closely.

Calcite can come in any color, but its streak is always white. How do you determine this? You need a streak plate for this. It is a small, unglazed porcelain tile with a rough surface. When you draw a line on it with a mineral, the streak color becomes visible; the act of drawing creates a fine powder of the mineral. This identification method is frequently used in mineralogy to distinguish between similar minerals. If a mineral varies in color but its streak remains the same, the mineral is said to be allochromatic (colored by impurities). Calcite is a prime example of this.

A mineral's density influences how heavy it is. This is best illustrated by comparing two identical candy jars: one contains three pieces of candy, while the other holds 100. Which one is heavier? That’s right—the jar with the 100 pieces of candy. It has a higher density, even though both jars look the same from the outside. The same applies to minerals: the higher the density, the heavier the mineral. Calcite has a density of 2.71 g/cm³.

Calcite can be dissolved in various liquids. It dissolves very well in hydrochloric acid; even a single drop causes the calcite to foam. In water, however, calcite dissolves only very, very slowly. Stalactites and stalagmites are good examples of this; the calcite is dissolved in the water and slowly crystallizes out with each drop. These formations grow by only 0.1 to 0.3 mm per year. It takes thousands of years for one to grow to a substantial size!