For the identification of a mineral it is necessary to know what are the properties that distinguish it, in fact each mineral is characterized by a series of properties that differentiate it from the others. It thus becomes necessary to be able to identify as many properties as possible, for some of them the verification is simple, such as the color of the smear or the hardness, for others it is required the use of expensive equipment, present only in laboratories specialized.


Hardness refers to the resistance opposed by a mineral to being scratched. There are two hardness scales, an absolute hardness scale, known as the Rosiwal scale, and an empirical hardness scale, known as the Mohs scale. This scale is made up of a series of ten very specific minerals, in which each mineral is able to scratch those that precede it and is scratched by those that follow it. It is also possible to evaluate the hardness of minerals practically: for example, minerals with a hardness of no more than 2 can be easily scratched with a fingernail, minerals up to grade 3 with a piece of copper, minerals up to grade 5 with a sharpener. with hardness 6 or higher they scratch the glass and are not scratched by steel points.

Smear color

The smear color is the color left by the mineral when it is rubbed onto a rough porcelain tablet. The color that is left by performing this procedure is characteristic for each mineral, moreover, regardless of the various shades that the mineral may present, the color of the smear will always be one. For example, fluorite is a mineral that can have shades of color ranging from yellow to green, to purple, to black, but the smear color will always be white. Of course, different minerals can have the same smear color.


The color of the minerals is due to a preferential absorption of various wavelengths among the innumerable that make up the spectrum of white light. The various colors of the minerals are linked to the presence of chromophores ions within the crystalline structure, such as iron, titanium and chromium. The coloration of minerals can also be due to distortions of the internal structure that alter the absorption capacity of certain wavelengths.

It is often led to believe that color is the most useful feature in recognizing a mineral, in reality in most cases this is not the case. In fact, a large part of minerals does not have a unique color but can have a high variety of colors. Furthermore, some minerals, in contact with the air, take on different colored patinas, it therefore becomes necessary to engrave the mineral so as to be able to observe the true color.


Luster is a property that indicates a mineral's ability to reflect light. The brightness depends on the relationship between the amount of light that is reflected and that which is refracted and absorbed.

Minerals that reflect almost all of the light that hits them, i.e. light does not pass through the mineral, turn out to be opaque. When light passes through the mineral and it is possible to see clearly what is behind it, the mineral is transparent.

This parameter is difficult to measure and for simplicity is described by analogy with common objects:

Vitreous luster, if it is similar to that of glass;

Metallic luster, if it matches that of shiny metal;

Picea luster, if it is similar to that of fresh tar;

Silky shine, if it is similar to that of natural silk illuminated by the sun's rays;

Greasy shine, if it is similar to oil stains on a white paper;

Adamantine luster, if it is very lively, as in the case of a polished diamond;

Pearly luster, if it recalls that present in the inner shells of many shells.

Flaking and Fracture

Flaking is the property that some minerals have to break down preferably in certain directions. For example, a mineral can flake along flat surfaces or divide into geometric portions.

If this preferential direction of failure is not evident, and therefore if the mineral breaks according to irregular surfaces, it is called a fracture. Depending on how these fracture surfaces appear, you can have a conchoidal, spathic, irregular or angular fracture.


Density, or specific gravity, is the ratio between the weight of a body and the weight of an equal volume of distilled water at 4 ° C. According to their specific weight, minerals are divided into:

Lightweight: specific weight <2;

Medium: 2 <specific weight <3;

Heavy: 3 <specific weight <6:

Very heavy: specific weight> 6