नवरत्नेषु वज्रं मुख्यम् । वज्रं षट्कोणं शुक्लवर्णम् - ऐन्द्रम् । असितं सर्पास्यसदृशं याम्यम् । नीलपीतं सर्पाकारं वैष्णवम् । स्त्रीमणिसदृशं वारुणम् । नीललोहितं कर्णिकारकुसुमसदृशं त्र्यस्रम् आग्नेयम् । यवाकारं मध्यस्थूलं लोहितवर्णमशोककुसुमसदृशं वायव्यम् ।

Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, but diamond is metastable and converts to it at a negligible rate under those conditions. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are used in major industrial applications such as cutting and polishing tools. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.