Fault
It is a split in the earth crust where the two sides may shift in opposing directions, resulting in an earthquake.

Feldspar
Any mineral belonging to the feldspar group.

Feldspar group
It is group of minerals of aluminum silicates which contains potassium, sodium, and/or calcium. This group of minerals is abundant on earth.

Feldspathoid
Any mineral belonging to the feldspathoid group.

Feldspathoid group
It is the group of minerals which are similar to feldspars. It lacks in the amount of silica to fully make them into feldspars while forming. As feldspars, they are aluminum silicates of potassium, sodium, and/or calcium. It is in the tectosilicates subdivision of the silicates group.

Ferromagnesian
It describes the rock-forming silicate minerals that contain essential iron (Fe) and/or magnesium (Mg). The very common ferromagnesian minerals include olivine, pyroxene, amphibole and mica.

Ferromagnetic
It is a term for greatly attracted to magnetic fields.

Ferromagnetism
It is referred to the magnetic property in certain materials which causes them to get attracted to magnetic fields.

Ferrous
Containing iron.

Fibrous
It is an aggregate which describes to a mineral constructed of fine and parallel (usually) threads. Some of the fibrous minerals can be bent around easily because of the cloth-like flexibility.

Flame test
It is test that is conducted to identify a mineral. It is a complex process. A tiny fragment of a mineral is placed at one end of a platinum wire and held in a flame. The change of the flame changes due to the presence of different metals like sodium will give yellow flame; copper, blue and green; potassium, violet; etc.

Flexible
Minerals which are capable of getting bent without breaking are said such. Flexibility is a form of tenacity.

Fluorescent lamp
It is a lamp which gives off ulraviolet light while blocking out white light, that causes fluorescent minerals to react.

Fluorite
It is a common mineral which comprises, in pure form, 51.1% calcium and 48.9% fluorine.

Fluorspar
The term is the commercial name for the mineral fluorite.

Fold
It is a bend in multiple rock layers.

Footwall
It is the name given to the host rock of an ore deposit which is physically below the ore deposit.

Fracture
It is the breaking of minerals when put under stress, beside cleavage.

Froth flotation
It is a process through which some mineral particles are induced to make it attached to the bubbles and thereby to float, while others sink. In this way, valuable minerals in an ore are separated from other components and concentrated.

Fusion
It is a process of being melted by heat.