Hornblende

Two samples of black Horblende with a vitreous lustre. The larger of the two samples shows part of the cleavage and the smaller of the two samples is a short, euhedral prismatic crystal with a diamond cross section. Hornblende ((Ca,Na,K)2-3(Mg,Fe2+,Fe3+,Al)5(Si,Al)8O22(OH)2) can be brown, green or black in colour and has either a submetallic, vitreous, pearly or silky lustre. Streak is colourless and hardness is 5 to 6. Cleavage is perfect in two directions forming a diamond shape. Hornblende is usually found as long or short prismatic crystals that have a diamond shape cross-section. Hornblende can also be granular, columnar, fibrous or radiated.