Very hard. Diamond has strong covalent bonds arranged in a rigid tetrahedral structure. Diamond is used in cutting tools for drilling through hard materials like rock and glass. High melting points ...

In diamond, each carbon atom is bonded to four other carbon atoms in a tetrahedral arrangement ... material to be diamond ...

The crystal structure is also known as diamond cubic and may be thought of as two interpenetrating ... The hexagonal wurtzite structure has the sulphur ions in an hcp array and one-half of the ...