Minerals

What are minerals? A mineral is a solid, natural material made from nonliving substances in the ground. Minerals are made up of elements. An element is a pure substance that cannot be broken down into a simpler substance. Examples of elements are gold, aluminum, oxygen, hydrogen, and iron. Some minerals are made up of a single element while others are made of two or more. Minerals are the building blocks of rocks.

What are the properties of minerals?

Luster Luster is the way a mineral reflects light from its surface. There are two general kinds of luster. Minerals with a metallic luster look shiny, while minerals with a nonmetallic luster look duller. Minerals with a nonmetallic luster may look waxy, pearly, earthy, oily, or silky.

Color Usually, we notice the color of a mineral first. Some minerals are easily identified by color because they are never any other color. For example, malachite is always green. Keep in mind, however, that color by itself isn't enough to identify a mineral.

For example, quartz in its purest form is colorless and clear as glass. Quartz with traces of iron becomes violet (amethyst). With traces of manganese, it turns pink (rose quartz). If quartz is exposed to radiation, it turns brown (smoky quartz).

Streak When a mineral is rubbed firmly across an unglazed tile of white porcelain (a streak plate), it leaves a line of powder. This is called the streak. The color of the streak is always the same, whether or not the mineral has impurities. For example, quartz leaves a white streak, whether it's violet (amethyst), pink (rose quartz), or brown (smoky quartz).

Hardness Hardness is a measure of how well a mineral resists scratching. A hard mineral resists scratching better than a softer mineral. On Mohs’ hardness scale, minerals are ranked from 1, which is the softest, to 10, which is the hardest. By scratching an unknown mineral with materials that have a known hardness, you can find the hardness of an unknown mineral.

Transparency Transparency describes how well light passes through a mineral sample. There are three degrees of transparency: transparent, translucent, and opaque. You can see objects through a transparent mineral. You can see light, but no objects through a translucent mineral. You can't see anything through an opaque mineral.

Cleavage When a mineral is broken, it breaks along planes of weakness that are part of its crystalline structure. These breaks are cleavages. The appearance of the surfaces of the mineral can help identify it. When the surfaces are smooth, the property that it has is cleavage. Cleavage is described by the number of planes along which the mineral breaks.

Fracture Fracture is the property a mineral shows when it has uneven or rough surfaces. Not all minerals cleave easily. Some fracture instead. Unlike cleavages, which are usually clean, flat breaks, fractures can be smoothly curved, irregular, jagged or splintery.

Crystal Form Minerals grow in specific shapes, and usually crystallize into one of six crystal systems. The axes of the crystal, the angles at which the axes intersect, and the degree of symmetry define each system. Different minerals have different crystal shapes.

Gems Some minerals, such as emeralds, are also called gems. A gem is a mineral that is rare, beautiful, usually transparent, and glitters or shines in light. While gems are often rough and uneven in their natural form, they can be cut into shapes to show their color and remove their flaws. After being cut and polished, many gems are used in jewelry.

Mineral Samples Pink – Feldspar White – Quartz Rough Black – Hornblende Smooth and Silvery - Mica