· Specific gravity of minerals
The specific gravity of a substance is the ratio between the weight of a given volume of that substance and the weight of the same volume of water.
Thus, if 1 dm3 2.65 kg weight quartz 1 dm3 of water and 1 kg weight, the specific weight of quartz is 2.65.
Measure the specific gravity of a mineral is sometimes desirable to distinguish from others that exhibit similar properties. The specific weight of a mineral depends on the kind of constituent atoms and their structure.
· The cohesion of minerals
Cohesion is the resistance of a body molecules to separate.
According to the degree of cohesion of a mineral, either in its entirety or in selected areas, properties distinguish these minerals: fragility, flexibility, delamination, fracture and toughness .
– A mineral is brittle when broken or sprayed with ease. Common salt is a fragile mieral.
– A mineral is pliable when folded easily (micas).
– A mineral exfoliates when applying on it the necessary strength, breaking into flats and parallel. The gypsum and graphite are minerals that easily exfoliate.
– A mineral is broken when, in applying the necessary force on it, it breaks into irregular faces. The quartz is fractured.
– The hardness of a mineral is the resistance of the mineral to be scratched., Hardness is a property useful for distinguishing minerals and each mineral is measured by comparing with those forming the Mohs scale . For example, if a mineral fluorite bay (hardness 4) and is lined by the apatite (hardness 5), its hardness is 4.5.
· Optical properties of minerals
When light falls on the mineral, can be reflected, absorbed or refracted specifically, according to the mineral on acting. This results in many and varied optical effects. The optical properties more easily observed in minerals are the color of reflection and refraction.
– The reflection color of a mineral (as any other object) is the result of mixing of the wavelengths of the light reflecting mineral.
– The refraction of a mineral is undergoing change light direction passing through the mineral. There monorrefringentes minerals , producing only a refracted ray and no birefringent minerals , which produce two refracted rays. Within the no uniaxial birefringent minerals (if they have a particular direction in which, by impinging light beam refracted give only) and biaxial (if they monorrefringencia two special directions.)