The Physical properties of minerals Are used by mineralogists to help determine the identity of a specimen. Some of the tests can be easily performed in the field, while others require laboratory equipment.
For the beginning student of the geology , There are a number of simple tests that can be used with a good degree of accuracy.
The list of tests is in a suggested order, going from simple experimentation and observation to more complicated either in procedure or concept (Amethyst Galleries, Inc., S.F.).
A mineral is an inorganic solid of natural origin that has a very characteristic internal atomic structure and a defined chemical composition.
Minerals can only be identified absolutely by means of X-ray analysis and chemical tests. X-ray analysis determines the structure of the mineral and chemical tests determine the composition of the mineral. Structure and composition are the defining marks of a mineral.
Unfortunately for the average collector, these tests require expensive equipment, expert knowledge, as they often destroy the sample.
Fortunately, both structure and composition affect certain physical properties. It is through proper use of these properties that minerals can be reliably identified (Properties of Minerals, S.F.).
Physical properties of minerals
Minerals possess many characteristics and physical properties that identify them. The most important are listed below.
Habit
In nature perfect crystals are rare. The faces that develop in a crystal depend on the space available for the crystals to grow.
If the crystals grow with each other or in a restricted environment, well-formed crystalline faces may not develop.
However, crystals sometimes develop certain forms more commonly than others, although symmetry may not be readily apparent from these common forms. The term used to describe the general shape of a crystal is habit (Nelson, 2013).
Color
Most minerals have a distinctive color that can be used for identification. In opaque minerals, color tends to be more consistent, so learning the colors associated with these minerals can be very useful in identifying.
Translucent to transparent minerals have a much more varied degree of color due to the presence of trace minerals. Therefore, color alone is not reliable as a unique identification feature (Bangert, S.F.).
Stripe
The stripe is closely related to color, but is a different property because the color of the mineral may be different to the color of the stripe. The stripe is actually the color of a mineral's powder.
It is called stripe because the proper way to test the stripe is to rub a mineral through an unglazed white porcelain tile and examine the color of the"stripe"left behind.
It has been shown to be a potent property because it is generally very consistent for a given mineral.
Two minerals that have a similar exterior color may have different colors when sprayed. For example, hematite and galena minerals may be confused when both have a gray color.
However, the hematite streak is red blood, while the galena streak is lead gray. Hematite (photo above) is probably the best-known example of the stripe with its striking color striking (Harder, 2013).
Hardness
This is an indirect measure of the bond strength in the mineral. It is exhibited as abrasion resistance on a relatively smooth and cool surface.
Friedrich Mohs (1773-1839) developed a relative scale of harnesses for the minerals we still use today.
Brightness
Gloss or shine is the property of minerals that indicates how much the surface of a mineral reflects light. The brightness of a mineral is affected by the brightness of the light used to observe the mineral surface.
The two main types of brightness are metallic and not metallic. Among the nonmetallic glosses we find the silky, clear, greasy, glassy resin and diamonds (Physical Properties of Minerals, S.F.).
Density
Density refers to mass per unit volume. The specific gravity is the relative density (weight of the substance divided by the weight of an equal volume of water).
In units cgs density is grams per cm 3 , And as the water has a density of 1 g / cm 3 , The specific weight would have the same numerical value as the density, but not units (units would be null).
Specific gravity is often a very diagnostic property for those minerals that have a high specific gravity.
In general, if a mineral has higher atomic number cations it has a higher specific gravity.
Cleavage and fracture
When a mineral breaks, it does so by fracture or by cleavage (or exfoliation). Crystalline cleavage is a smooth break which produces what appears to be a flat crystalline face. Here are some rules about division.
The first division is reproducible, which means that a crystal can break along the same parallel plane, over and over again.
All the division must be parallel to a possible glass face. This means that the crystal could have a crystalline face parallel to its cleavage, but these faces do not always form.
All the planes of division of a mineral must coincide with the symmetry of that mineral. And, finally, the same mineral always, always has the same division.
The fracture describes the quality of the cleavage surface. Most minerals present irregular or granular fractures, conchoidal (curved, shell shaped) fractures or aggressive (rough, dentate) fractures (Physical Properties of Minerals, S.F.).
Tenacity
Tenacity is the resistance of a mineral to breaking, crushing or bending. Tenacity can be described by the following terms.
- Fragile - It breaks or burns easily.
- Malleable - can be hammered into thin sheets.
- Séctil - can be cut into fine chips with a knife.
- Ductile - folds easily and does not return to its original shape.
- Flexible - fold something and not return to its original shape.
- Elastic - bends but returns to its original shape
Transparency or transparency
The transparency is the degree of transparency or ability of a mineral to allow light to pass through it. The degree of transparency may also depend on the thickness of the mineral.
References
- Amethyst Galleries, Inc.. (S.F.). THE PHYSICAL CHARACTERISTICS OF MINERALS . Retrieved from galleries galleries.com.
- Bangert, A. (S.F.). Physical Characteristics of Minerals . Retrieved from dave.ucsc.edu: dave.ucsc.edu.
- Harder, V. (2013). Mineral Properties . Retrieved from mineralogy4kids: mineralogy4kids.org.
- Nelson, S.A. (2013, September 16). Physical Properties of Minerals . Retrieved from tulane.edu: tulane.edu
- Physical Properties of Minerals. (S.F.). Retrieved from people.carleton.edu: people.carleton.edu.
- Physical Properties of Minerals . (S.F.). Retrieved from people.carleton.edu: people.carleton.edu.
- Properties of Minerals . (S.F.). Retrieved from rocksandminerals4u: rocksandminerals4u.com.