Physical properties

An initial step in identifying a mineral is to examine its physical properties, many of which can be measured on a hand sample. These can be classified into density (often given as specific gravity); measures of mechanical cohesion (hardness, tenacity, cleavage, fracture, parting); macroscopic visual properties (luster, color, streak, luminescence, diaphaneity); magnetic and electric properties; radioactivity and solubility in hydrogen chloride (HCl).[3]:97–113[6]:39–53
An example of the mineral, which possesses strong magnetic properties is the mineral magnetite, lodestone, from Tortola, British Virgin Islands; found in igneous plutonic rocks[7] formations, composed of several minerals, including quartz, plagicase, alkali feldspar, biotite and titanite.[8]
If the mineral is well crystallized, it will also have a distinctive crystal habit (for example, hexagonal, columnar, botryoidal) that reflects the crystal structure or internal arrangement of atoms.[6]:40–41 It is also affected by crystal defects and twinning. Many crystals are polymorphic, having more than one possible crystal structure depending on factors such as pressure and temperature.[3]:66–68[6]:126
Polymorphism in crystallography, the condition, when the mineral of a single solid chemical composition, can have more than one crystal structure, however the results of the research work of the scientists from the University of Bristol in 2016, proved that polymorphism can be controlled, what is opening a new way to grow crystals: Dr Hall said: “The application of magnetic fields to intentionally control polymorphism is entirely novel...”[9] Examples of polymorphs are calcite and aragonite – two minerals with identical chemical composition, distinguished by their crystallography: calcite is rhombohedral and aragonite is orthorhombic.

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Chemical elements

A few minerals are chemical elements, including sulfur, copper, silver, and gold, but the vast majority are compounds. Before about 1947, the main method for identifying composition was wet chemical analysis, which involved dissolving a mineral in an acid such as hydrochloric acid (HCl). The elements in solution were then identified using colorimetry, volumetric analysis or gravimetric analysis.[13]:224–225 A variation on the wet methods is atomic absorption spectroscopy, which also requires the dissolution of the sample but is much faster and cheaper than the above methods. The solution is vaporized and its absorption spectrum is measured in the visible and ultraviolet range.[13]:225–226 Other techniques are X-ray fluorescence, electron microprobe analysis and optical emission spectrography When light passes from air or a vacuum into a transparent crystal, some of it is reflected at the surface and some refracted. The latter is a bending of the light path that occurs because the spee...
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Alloys

Common engineering metals include aluminium, chromium, copper, iron, magnesium, nickel, titanium and zinc. These are most often used as alloys. Much effort has been placed on understanding the iron-carbon alloy system, which includes steels and cast irons. Plain carbon steels (those that contain essentially only carbon as an alloying element) are used in low-cost, high-strength applications where weight and corrosion are not a problem. Cast irons, including ductile iron, are also part of the iron-carbon system. Stainless steel or galvanized steel is used where resistance to corrosion is important. Aluminium alloys and magnesium alloys are used for applications where strength and lightness are required. Copper-nickel alloys (such as Monel) are used in highly corrosive environments and for non-magnetic applications. Nickel-based superalloys like Inconel are used in high-temperature applications such as gas turbines, turbochargers, pressure vessels, and heat exchangers. For extremely hi...
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