Physical properties of the minerals

The physical properties of minerals are essential to be able to identify them. Some of these properties can be determined with the naked eye (visu) and others by very simple tests.

Depending on the chemical composition and structure of the mineral, it will have some properties or others. It must be taken into account that in nature, a mineral can have some contamination, mixture or structural defect that makes its characteristic properties several.

The main physical properties of minerals are:

• The density.
• The magnetic properties.
• The electrical properties.
• The form and the habit.

Density

The density  is the ratio of the mass of mineral  and the volume it occupies. It is usually expressed in g/cm³.

According to their density, minerals are classified into:

• Light minerals: Their densities are less than 2.5 g / cm³.
• Normal minerals: Their density is between 2.5 and 4 g/cm³.
• Heavy minerals: Their density is greater than 4 g/cm³.

Although we cannot directly know the value of the density of a mineral specimen, it can help us to identify it simply by weighing it by hand.

Density is a highly reliable data for the determination of minerals. For example, it can be of great help to us to identify barite  or galena.

Magnetic properties of minerals

Some minerals have magnetism. This property causes some minerals (generally containing iron, cobalt or nickel) to be attracted to a magnet.

According to their magnetic properties, they are distinguished:

• Ferromagnetic minerals: These are minerals that are strongly attracted to a magnet, such as magnetite.
• Paramagnetic minerals: They are minerals that are weakly attracted by a magnet, such as hematite and siderite.
• Diamagnetic minerals: These are minerals that are not attracted to the magnet, such as sulfur and quartz.

Electrical properties of minerals

Conductivity

The conductivity is the property that some minerals that allow the passage of electricity, so it can transmit electrical current.

Good conductors of electricity are native metals, sulfides, and metal oxides. But most minerals are poor conductors of electricity.

Pyroelectricity

The pyroelectricity is the electric charge having the faces of some crystals are subjected to a temperature variation. The tourmaline  and topaz are pyroelectric minerals.

Piezoelectricity

The piezoelectricity is the property that some minerals that causes when they are under pressure, they acquire loads of opposite sign at their ends.

For example, quartz can generate sparks when struck.

Form and habit of minerals

The crystalline habit describes the general appearance of minerals. The habit is determined by the environmental conditions of formation and is a reflection of the crystalline structure, which has its shape. The same mineral can appear under different habits.

Thus, the crystalline habit can be:

• Prismatic, when the crystals have short elongated shapes.
• Acicular, with crystals with elongated prismatic forms like needles.
• Filiform, with crystals in the shape of threads or hairs.
• Tabular, in the form of tables or sheets.
• Etc.