minerals. what are minerals? a mineral is a solid, natural material made from nonliving substances...
TRANSCRIPT
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