EOSC 118 Lecture Notes - Lecture 9: Hope Diamond, Crystal Chemistry, Thermal Conductivity
4 Aug 2015
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Document Summary
Diamond is pure carbon packed into a dense crystalline structure (3. 51 g/cm3) with cubic symmetry and perfect octahedral cleavage. Pure diamonds are colourless but defects, elemental substitutions and lab procedures allow them to be shown in the full range of colours in the rainbow. Diamonds have few extra physical characteristics: thermal and electrical conductivities: high thermal conductivity due to covalent bonding that holds c atoms together, 3 times higher than gold &silver. The low electrical conductance paired with high thermal conductance is unusual. The simulant moissanite is a semiconductor and will pass electricity more. It also has similar thermal conductivities as diamonds. Belongs to the isometric/cubic crystal system: each of the crystallographic axes is same length and at 90 degrees to one another. Graphite has same chemical composition as diamond ( c ), but has a different crystal structure, therefore has different physical properties: this is known as polymorphism (same composition but different crystal structure)
