What is the Difference Between Biotite and Hornblende?

Biotite and hornblende are both dark-colored silicate minerals, but they have different structures and properties. The main differences between biotite and hornblende include:

1. Structure: Biotite is a sheet silicate, where the silica units (SiO4) form continuous sheets, which is why micas (of which biotite is one) split into thin sheets. Hornblende, on the other hand, is an amphibole, a chain silicate, where the silica units form pairs of linked chains with other atoms in between.
2. Chemical Composition: Biotite is a phyllosilicate mineral in the mica group with the chemical formula K(Mg,Fe)3AlSi3O10(F,OH)2. Hornblende is a complex inosilicate series of minerals.
3. Cleavage: Biotite forms perfect shiny black cleavages and can be peeled into flakes. Hornblende does not flake.
4. Appearance: Biotite is shinier than hornblende.

In summary, biotite and hornblende are both dark-colored silicate minerals, but they differ in their structure, chemical composition, cleavage, and appearance. Biotite is a sheet silicate mineral with a perfect shiny black cleavage, while hornblende is a chain silicate with a darker appearance.

Comparative Table: Biotite vs Hornblende

Here is a table comparing the differences between biotite and hornblende:

Biotite is a phyllosilicate mineral in the mica group, while hornblende is a complex inosilicate series of minerals. The main difference between the two lies in their chemical compositions and crystal structures. Biotite easily forms perfect shiny black cleavage and can be peeled into flakes, whereas hornblende does not flake. Both minerals are associated with silicate functional groups and are found in various types of igneous rocks.