Boron

Physical properties


Physical state @ 20°C: Solid [5]
Color: α-rhombohedral structure: Clear red crystals [7]
β-rhombohedral structure: Black [7]
α-tetragonal structure: Black, opaque with metallic luster [7]
Amorphous form: Black or dark brown [7]
Odor: Odorless [5]
Molecular weight (g/mol): 10.811(7) [2]
Melting point (°C): List of melting points 2092 [2]
Boiling point (°C): List of boiling points 4002 [2]
Ignition temperature (°C): 700 [5]
Density (g/cm3): Density list α-rhombohedral structure: 2.46 [7]
β-rhombohedral structure: 2.65 [7]
α-tetragonal structure: 2.31 [7]
Amorphous form: 2.350 [7]
Hardness:
Mineral hardness:

11 [2]
Solubility: Water: Insoluble (20 °C) [5]