TRANSVERSE CONTRACTION JOINTS. The primary purpose of transverse contraction joints is to control the cracking that results from the tensile and bending stresses in concrete slabs caused by the cement hydration process, traffic loadings, and the environment.
Diamonds are found in igneous rock which is brought to the surface of the earth by volcanic eruptions bringing magma to the surface. Diamond itself is strictly an allotrope of the element carbon, a mineral, one form of crystal that can be created from carbon.
Obsidian is an igneous rock that forms when molten rock material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure.It is an amorphous material known as a  mineraloid ..bsidian is an igneous rock that forms when molten rock material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure.