MINING ROCKSTAR OF THE WEEK – HORNBLENDE!!

Hornblende is a field and classroom name used for a group of dark-colored amphibole minerals found in many types of igneous and metamorphic rocks. These minerals vary in chemical composition but are all double-chain inosilicates with very similar physical properties. A generalized composition for the hornblende group is shown below.

(Ca,Na)2-3(Mg,Fe,Al)5(Si,Al)8O22(OH,F)2

Note that calcium, sodium, magnesium, iron, aluminium, silicon, fluorine and hydroxyl can all vary in abundance. This creates a huge number of compositional variants. Chromium, titanium, nickel, manganese, and potassium can also be part of the complex composition and further indicates the generalization of the formula given above - "Geology.com"