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Hornblende

Hornblende

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Although, there are large numbers of minerals which differ in all aspects, some specific minerals are hard to distinguish via physical means. These minerals are then grouped and given a common name. Hornblende is a compound name given to a group of minerals that are similar in specific physical properties. These minerals include Ferro hornblende, Magnesio-hornblende, Alumina Magnesio hornblende and alumina-ferro-hornblende.

The name "Hornblende" was gotten from "horn" and "blenden" meaning "deceive" due to its similar appearance with other metals that contain ore mineral deposits. It is a mixture of the following silicates: Aluminium-iron-magnesium silicate, iron-magnesium silicate and calcium-iron-magnesium silicate, having the molecular formula (Ca, Na)2-3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2.

Hornblende is not usually attractive due to its translucent nature and black colour. Despite this fact, some specimens are extraordinary and precious due to their large size.

Other characteristics of Hornblende:

- The Basaltic hornblende, which contains basalt, and other similar rocks is usually dark brown or black because it contains titanium.

-The Edenite hornblende, which originates from Edenville, New York, is rare and is usually gray or white. This is due to the fact that its constituent, iron oxide is less than 5%.

-Its lustre can be vitreous or dull.

- In general, hornblende crystals are opaque but the translucent ones are thin crystals.

- The hornblende crystals, which are short and stocky, are frequently prismatic.

- It has an uneven fracture and imperfect cleavage.

- The crystals usually have a brown or gray colour with a grainy look.

- Other minerals associated with hornblende include augite, feldspars, magnetite, quartz, micas, etc.

- Due to its black colour, hornblende is sometimes mixed up with biotite mica and augite which are also found in granite.

The hornblende is a primary mineral of amphibolites and is a widespread constituent of some metamorphic and igneous rocks such as the syenite, schist, diorite, granite and basalt.

Additional Resources

Greisen   Igneous Rock   Iron Oxide

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