All About Minerals

• Minerals are the building blocks of rocks.
• Minerals are inorganic elements present in soil and water, which are absorbed by plants or consumed by animals.

Characteristics of Minerals

• They occur naturally as part of earth's natural processes.
• They are inorganic, meaning they are not a product of an organism or come from living matter.
• Minerals have a definite volume and rigid shape.
• They have an orderly crystalline structure where atoms are arranged in an orderly and repeating pattern.

Physical Properties of Minerals

• Color is the most obvious but often misleading way to identify a mineral and is the least useful because many minerals have similar colors.
• Different colors may result from impurities, or they can change colors due to different circumstances.
• Color is the first thing someone notices when they view a mineral.
• Color is one of the big reasons that attract people to minerals.

Example Quartz

• Quartz is the most common mineral.
• Quartz is made of the two most abundant chemical elements on Earth: oxygen and silicon.
• Quartz becomes colored with the presence of other minerals or growth imperfections.
• Milk quartz is the most common variety of crystalline quartz, and its white color is caused by minute fluid inclusions of gas, liquid, or both, trapped during crystal formation.
• The smoky color results from free silicon formed from the silicon dioxide by natural irradiation.
• The quartz variation amethyst has iron impurities.
• The quartz variation citrine gets its yellow color from aluminum.
• Rose quartz is a type of quartz that exhibits a pale pink to rose-red hue, and the color is usually considered due to trace amounts of titanium, iron, or manganese in the material.

Streak

• Streak is the color of a mineral in powdered form.
• Cinnabar looks grey, but always produces a light-brown streak.
• Hematite looks black, but always produces a red-brown streak.
• Gold leaves a yellow streak, and pyrite will leave a greenish-black streak, which can be used as a test to see if you have pure gold or pyrite.

Hardness

• Hardness is a measure of a minerals relative resistance to scratching.
• Mohs scale of mineral hardness is a scale to measure relative resistance to scratching.

Cleavage and Fracture

• Cleavage is the tendency of a mineral to break along smooth planes parallel to zones of weak bonding.
• Fracture is the tendency of a mineral to break along curved surfaces without a definite shape.
• Minerals that fracture do not have planes of weakness and break irregularly.
• Cleavage planes are smooth, flat, parallel planes within the crystal.
• Cleavage planes may show as reflective surfaces on the crystal, as parallel cracks that penetrate into the crystal, or show on the edge or side of the crystal as a series of steps like rice terraces.
• Fracture is different than cleavage in that the broken surface will not be flat or even.
• The breakage does not occur along a distinct plane within the crystal in fracture.

Diaphaneity/Transparency

• Diaphaneity/transparency is the ability to allow light to pass through.
• Describes how well light passes through a mineral.
• There are 3 degrees of transparency: transparent, translucent, and opaque.
• Transparent allows light to pass through.
• Translucent depends on thickness and the light may or may not pass through or be absorbed.
• Opaque doesn’t allow light to pass through.

Luster

• Luster is how light is reflected off a surface.
• It is the appearance of a mineral surface in terms of its light-reflective qualities.
• Luster depends upon a mineral's degree of transparency.
• There are two types: metallic and nonmetallic.
• Metallic luster looks like shiny metal such as chrome, steel, silver, or gold.
• Metallic minerals are always opaque.
• Non-metallic minerals may be shiny and reflect light, however, they do not look like a metal.

Metallic Luster Examples

• Just like metals they reflect light

Non-Metallic Luster Types & Examples

• Dull or Earthy minerals shine minimally to none.
• Waxy minerals shine like wax.
• Vitreous or Glassy minerals shine like broken glass.
• Silky minerals shine like silk.
• Pearly minerals shine iridescently, like a pearl.

Tenacity

• Tenacity describes the reaction of a mineral to stress such as crushing, bending, breaking, or tearing.
• Minerals react differently to each type of stress and it is is possible for a mineral to have more than one type of tenacity.

Tenacity Classification

• Brittleness is when a mineral turns into powder when hammered.
• Malleability is when a mineral can be flattened by pounding with a hammer.
• Ductility is when a mineral can be stretched into wire.
• flexible but inelastic minerals are bent but they remain in the new position after they are bent.
• Flexible and elastic minerals return to their original position after stress is released.

Sectility

• Sectility is the ability of minerals to be sliced by a knife.