According to Nickel E.H. Of 1995,"A mineral is either a chemical compound or an element, usually found in the crystalline structure, which is an outcome of the ecological course of action” .
According to O’Donoghue of 1990, Minerals occur in nature as substances that are inorganic, Their chemical composition and physical properties are predictable and exact”.
According to Mason et al of 1968,“A mineral occurs in nature as a solid that is homogenous and formed inorganically, Its chemical composition is exact with a disciplined orientation of its atoms”.
According to Sinkankas of 1966 “Each mineral has its own properties by which it is discriminated from one another. These discrete properties occur in accordance with their type of atom and their configuration within the element.
According to Dana & Ford of 1932,”A mineral is a substance composed of naturally occurring inorganic processes that have a precise chemical composition, combined under ideal circumstances, along with its physical properties, assurance of its traits is conveyed by its crystalline structure.
According to Brush & Penfield of 1898, each distinctive chemical compound that occurred in nature inorganically with a precise orientation of its molecular structure or the order of crystallization and clearly specified physical properties, makes the variety of mineral”
Minerals- Physical Properties
Mineralogists identify a particular specimen of mineral with the help of its physical properties. It is possible to conduct certain tests where it is obtained, whereas many other tests are needed with special laboratory equipments. For a beginner in geology, many simple tests are available, which results in a high level of precision. The series of tests are performed in a systematic manner, starting from ordinary experiments and observing the results leading to more intricate tests.
A mineral is identified by the aforesaid physical properties:
Cleavage of Fracture
Diaphaneity or Transparency value
The properties of every mineral are clearly described as follows:
Detailed Description of mineral properties
The majority of the minerals possesses distinct color by which they are identified. The minerals that are opaque have a tendency of consistency in their color.. The color variations of the transparent to translucent minerals are vast on account of the trace minerals present in it. Hence we cannot depend on color as a measure of identifying their properties.
The pulverized mineral color is called a streak. This displays the exact minerals exact color. In bulk solid structure, the trace mineral color changes with light reflection in a particular form. The powdered constituents of a streak of the trace minerals induce a minute effect on the reflecting light.
The streak in metallic minerals is inclined to seem deeper in color on account of the absorption of the reflecting light on the small streak constituents. The constituents that are not metallic have an inclination to reflect the majority of light and thus they look a paler color or more or less white.
The streak is very precise in illustrating the mineral’s color. The streak offers a highly dependable property of the mineral when compared to color discrimination.
Minerals are better identified by their hardness. Hardness represents the property by which it is possible to measure the resistance of the mineral to scratching. This is checked on the Mohs scale that has 10 sets of minerals with known hardness. Talc, which is the softest of the minerals, has a Mohs rating of 1. The rating of Diamond which represents the hardest of the mineral is ten. Harder minerals are used to scratch softer minerals, since their binding force is weaker, which the mineral that is harder, can easily break.
Fracture & Cleavage
When struck with force, there is a tendency for the minerals to shear along smooth surfaces or along the lines. The fractures of various types of minerals are diverse which exhibits varied cleavage patterns.
Two different criteria sets are used to define cleavage. The quickness of obtaining cleavage is explained by the primary criteria set. If cleavage is attained with ease, it is regarded as perfect. Besides, its cleavage planes appear conspicuous. If in case cleavage is acquired with difficulty, it is regarded as excellent, provided you have clear cleavage planes. In conclusion, it is regarded as imperfect in case cleavage is attained with complication and certain planes are not easily identified.
The track of the surface cleavage is obtained by the second criteria set. According to the cleavage surface’s form, there are named as Rhombohedral, Cubic, Dodecahedral, Octahedral, Prismatic or Basal. It is the particular cleavage lines, angles that give the definition of the criteria.
Cleavage Type Angles
Cubic cleaves appear @ 90o to each other in three directions, the Rhombohedral type also cleaves in 3 directions, but do not achieve 90o to each other, Octahedral cleaves in 4 directions, Dodecahedral cleaves in 6 directions, Basal in 1 direction and Prismatic in 2 directions.
The class of cleavage surface is determined by the fracture of the mineral. The majority of minerals exhibit either grainy or uneven fracture, hackly fracture (rough, jagged) or Conchoidal fracture (curved, lines like a shell).
The crystals of mineral are formed in different sizes and shapes, according to the orientation of the molecules, ions or atoms; it is possible to specify a crystal shape and their bonding. Such an arrangement is what crystal lattice is. The crystalline structure occurs in different degrees, where the crystal fibers become complicated or rather difficult to glance with your naked eye, and difficult even by using a hand lens. It is possible to have a view of the Crystalline and Microcrystalline structures only through powerful magnification. Minerals with no definite crystalline structure are called amorphous. But the number of amorphous crystals is limited which are viewed only by using very high magnification.
The capacity to permit light to traverse through it or the transparency percentage of a mineral is called Diaphaneity, which varies according to the mineral’s thickness.
The property by which the particle is bonded in the mineral is called tenacity or otherwise it is the resistance of the particles in a mineral to separate.
A mineral’s property to repel or attract materials that are magnetic is called magnetism. It is cumbersome to identify the magnetic strength of different minerals, however, having a knowledge of the dissimilarities is an asset.
An indication of the extent to which a mineral’s surface reflects light is the property of the mineral called luster. The shine of the mineral is influenced by the light’s brightness with which one views the surface of the mineral.
Metallic property means, opacity of the mineral in nature and reflects light just like metals do. Sub-metallic property means the mineral appears dull, opaque and dark in color. Nonmetallic means the mineral never reflects light just like metals do.
Modifiers which represent the general qualities are used to illustrate nonmetallic minerals.
Waxy minerals resemble wax or paraffin. Vitreous minerals resemble shattered glass. Pearly minerals resemble oil poured on water. The resinous mineral resembles the resin of tree sap that is hardened. Adamantine mineral resembles brilliance like the diamond.
The majority of minerals occurred in nature are odorless, except when they are either heated, moistened or rubbed against something.
Only minerals that are soluble possess taste; however, it is imperative that minerals are never placed either on the tongue or in the mouth. Neither should you test this quality in your classroom
Density (Specific Gravity)
A mineral density or specific gravity is a relation of the ratio of its weight to the mass of the same quantity of water. By determining the difference in weights of mineral in water and the same quantity in the air, it is possible to find the weight of the same quantity of water.