Calcium carbonate Museum

CaCO3 Properties

Water-soluble mineral

As mentioned earlier, because calcium carbonate is a water-soluble mineral, create a singular topography just like Karst. Chemical Properties which CaCO3 dissolve into water is different from other minerals. CaCO3 does not dissolve into tap water, but it is easy to dissolve into acid water. For example, if you blow a breath(it contains CO2) onto calcium solution, you can see white calcium carbonate precipitation. But if you keep blowing the solution become aerated water, then precipitated CO3 dissolve into water again. This is the lime stone encroaching mechanism in nature.

Shape of CaCO3

Calcium carbonate
Calcium carbonate (CaCO3) is composed of carbonate ion (CO3 ion) and calcium ion (Ca ion). Usually calcium carbonate is a white rock (or powder), but if you enlarge CaCO3 to the numerator level, you could see a figure like right picture. Besides you’d better know that mined limeston is not a 100% calcium carbonate but contained a little impurities.
Many calcium carbonate molecules are gathered together, our eyes can catch their shape. A way of gathering determine their properties. This way of gathering is called “Crystal structure”. Calcium carbonate have three types of crystal structures as indicated next table. “Calcite” is most stable crystal structure, so almost lime stone is calcite which out put from mines.
    Calcite Aragonite Vaterite
  Crystal structure Trigonal Orthorhombic Hexagonal crystal
Mineral Properties Hardness 3 3.5 - 4 3
A refractive index 1.49 - 1.69 1.53 - 1.69 1.56 - 1.66
Specific gravity 2.7 2.9 2.5 - 2.6
Calcite
Aragonite
Source: Celestite Blue HP
(http://www.geocities.jp/celestine_blue_sky/)
High temperature and pressure generated by diastrophism melted a part of coral reef Calcium carbonate. Melted calcium carbonate was cool down very slowly and finally several types of crystals had been formed. Cool down speed and impurities affect the shape of crystals.

CaCO3 groups

Heavy calcium carbonate Calcium carbonate which limestone crushed. CaCO3. 
Precipitated calcium carbonate A synthetic calcium carbonate reacts with slaked lime and carbon dioxide. CaCO3.
Quick lime Roast limestone and remove CO2 at high temperature(more than 900℃) .CaO
Slaked lime Calcium hydroxide which react with quick lime and water. Ca(OH)2
  • Calcium carbonate Museum
  • Where CaCO3 came from?
  • CaCO3 Properties
  • CaCO3 in our life field
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