Physical Properties of Rock

The solid aggregation of minerals, of which the Earth's outer solid layer, also known as lithosphere, is commonly known as rock. I like to share this Permanent Magnet AC Motor with you all through my article.


Types of Rocks

On a broader scale, there could be outlining three  categories of rocks. This classification is done on the basis of the formation of these rocks. Rocks could, therefore, either be

Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
The study of rocks is called petrology and is an essential part of geology.

Another important fact that characterises a rock is its size properties. Normally, a mineral material with size exceeding 2 mm in dimension is categorized as a rock whereas the one below that is nothing but a soil particle.  Certain very noticeable features of a rock include:

its non contribution to the soil in terms of nutrients, except a few minutest amounts.
its non capability to hold water for availability to the plants
its toughness on any tilling equipment.

Physical properties of rock:

Rocks comprise of one or more minerals. . Minerals may broadly be pure, solid, inorganic materials found in Earth's crust and generally comprise of one or more elements. Minerals are made of one or more elements which are the most basic, naturally occurring substances on Earth. Elements, generally, cannot be broken down. A few of the very basic properties of elements are mentioned below:

Color

Color is one of the most basic identifiers in identifying a mineral. But then there are always some minerals which are supposed to have more than one color, say for example, Quartz, which can occur in blue, brown, pink, red, purple and almost any other colour, in fact, sometimes colorless as well. The property of identifying a mineral with color is called a streak.

Streak

Streak refers to the colored residue left by scratching a mineral across an abrasive surface, such as a tile of unglazed porcelain. A mineral with more than one color will always leave a certain color of streak. For example, Hematite is a mineral that can be seen in red, brown or black, but it will always leave a characteristic reddish brown streak.

Luster

Luster is the shining property of a mineral. There are two types of luster:

Metallic
Nonmetallic
A metallic luster is shiny and similar to the reflection from a metal object, such as a faucet.

A mineral that does not shine like metal has a nonmetallic luster. For example, the wall has a nonmetallic luster.

There are many types of nonmetallic luster.

A glassy luster is bright and reflects light like a piece of glass.
A greasy luster has an oily appearance.
An earthy luster is a very dull and looks like dirt.
A Waxy luster looks like the shininess of a crayon.

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Physical properties of Rock(Continued)


Cleavage

One of the tendencies of minerals is to break along flat planar surfaces. This property is known as Cleavage. Experts use even this property to classify the minerals. Cleavage is generally indicated with the help of rating is good, fair and poor depending on the flat surface produced.

For instance, Mica is supposed to have a good cleavage. It breaks into very flat sheets.

Minerals having very poor cleavage will only break along irregular surfaces.

For example, Quartz will break into pieces that have a seashell-like fracture plane. Others, like garnet, shatter will have no distinguishable pattern. These are considered to have no cleavage at all.

Hardness

Another important property that scientists use to classify minerals and identify them is the degree of hardness f that mineral where this degree may vary between 1 to 10, 1 being the softest mineral (talc) and 10 being the hardest (Diamond).