Laacher See Volcanic Complex, Germany

Al₂O₃

Crystal System: trigonal
Colour: colourless, blue, red, pink, yellow, grey and golden-brown
Lustre: adamantine, vitreous, pearly
Habitus: prismatic, often bipyramidal
Hardness: 9
Fracture: irregular/uneven or conchoidal
Cleavage: none
Density: 3.997 g/cm³ 
Origin and geological occurrence: corundum is characteristic of Al-rich and Si-poor geological environments. It has been found in contact aureole between intrusive sialic rocks and calcareous-clay rocks. Thanks to its hardness, corundum can be found in placers as residual mineral that overcomes the weathering.

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Samples:

	4.3 Corundum Pseudo-hexagonal reddish crystal. #oxides
	4.4 Corundum Pseudo-hexagonal tabular pinkish crystal.