Plaster, Cement, Bricks

Plaster has a formula: (CaSO4)2.H2O and is able to absorb (slowly) lots of water. When mixing water free (dry) plaster with water, at the beginning the mixture will be a misture of (l) + (s), but after building in the water(l) into the solid, you stay with a solid: hydrated plaster (hard matter).

(CaSO4)2.H2O(s) +  3H2O(l) 2CaSO4.2H2O(s)
the raw material for cement is a mixture of Calcium carbonate + Alluminiumoxydes + SiliciumOxydes. You must heat the mixture very intensly, then first the carbonate will change into CaO.
At temperatures above 1500ºC reactions occur between those oxydes of Calcium, Aluminium and Silicium, ans salts are made like silicates and aluminates of Calcium, often still in the presence of Iron. The final mixture is very well grinded and sold als Portland Cement.
this cement is extremely hygroscopic. With water it forms a mixture that within minutes becomes extremely hard.

On our planet we have enormous amounts of water. The following substance in abundance after water is sand, with the main component SiO2. The other components are, for example, compounds of Iron (gives sand the brownish color) and compounds with aluminium. Apart from Silicium oxyde, also silicates are present in earth.

Clay also contains silicates of Aluminium: silicate compounds where part of the Si-atoms are substituted by Al-atoms.
Clay has a kind of folded structure, caused by macromolecules. They have a two-dimensional structure and can - in the presence of water - easily move over each other. That's why clay feels slippery.
But, if you heat clay very strongly (bake) the water molecules disappear, the folded layers come very close toghether and will create threedimensional connections. A very hard structure is the consequence: brick and ceramics in various qualities.