Mineral Properties

Key Concepts A pure substance, such as a mineral, can be identified from observations and tests performed to determine its physical properties. These properties are based on the unique structure of the substance. Minerals are crystals that form naturally in the Earth. They have characteristic properties, such as color, hardness, and a crystalline shape. Rocks are made of minerals.

General Vocabulary Geologist – scientist who studies the Earth and the changes that take place on and beneath the surface Rock – a naturally occurring solid substance composed of one or more minerals.

General Vocabulary Mineral – a naturally occurring solid material that has a specific chemical composition and crystal form and characteristic physical properties. There are about 3,800 different minerals.

General Vocabulary Mineral Characteristics: Forms in nature Is a solid Has a definite chemical make-up Has a crystal structure

Mineral Characteristics Forms in nature Is a solid Has a definite chemical make-up Has a crystal structure Formed by natural processes. It has been estimated that garnets can grow about one atomic layer per year (a two centimeter crystal growing over a period of ten million years) Are inorganic which means they are made of non-living materials found naturally on earth.

Mineral Characteristics Forms in nature Is a solid Has a definite chemical make-up Has a crystal structure A mineral has a definite volume and a rigid shape. Volume refers to the amount of space an object takes up

Mineral Characteristics Forms in nature Is a solid Has a definite chemical make-up Has a crystal structure Every mineral consists of a specific combination of atoms of certain elements. The types of atoms that make up a mineral are part of what makes the mineral unique. The way in which the atoms are bonded, or joined together, is also important. Many properties of minerals are related to how strong or weak the bonds are.

Mineral Characteristics Forms in nature Is a solid Has a definite chemical make-up Has a crystal structure Each mineral has its own type of crystal structure. Minerals can have the same chemical compound/same type of atoms, but the way the atoms are arranged is different. Diamonds and graphite are made of the same element, carbon, but the arrangement of these carbon atoms is different.

Side Note… …look at the following minerals: Which do you think are the same types of minerals and which do you think are different?

TRICK QUESTION!!! These are all the same type of mineral! They are all examples of quartz!!

Why Is It So Difficult to Identify Minerals? There are over 3800 types of minerals in the Earth’s crust As you could see with the quartz, often times even the same kind of minerals can look very different Therefore, geologists (scientists who study minerals and rocks) often use several different tests to determine type of a mineral they have found!

Mineral Properties Cleavage & Fracture Color Luster Minerals have characteristic properties that are used to identify them: Color Luster Transparency Streak Cleavage & Fracture Crystalline Structure Texture Hardness

Mineral Properties Color Luster Transparency Streak Cleavage & Fracture Crystalline Structure Texture Hardness Color is obviously one of the most noticeable characteristics of a mineral, but it also the least reliable of all the characteristics The color of a mineral is often caused by tiny amounts of other elements or compounds inside For example, what people call amethyst is actually just quartz with iron in it!

Mineral Properties Color Luster Transparency Streak Cleavage & Fracture Crystalline Structure Texture Hardness The way that a mineral reflects light from its surface is its luster The two types of luster are: - metallic - nonmetallic

Mineral Properties Color Luster Transparency Streak Cleavage & Fracture Crystalline Structure Texture Hardness A mineral’s degree of transparency: ability to allow light to pass through it. The degree of transparency may also depend on the thickness of the mineral. Also known as “Diaphaneity”

Mineral Properties Color Luster Transparency Streak Cleavage & Fracture Crystalline Structure Texture Hardness When a mineral is rubbed against a tile, it will leave behind a colored powdered streak on the tile Sometimes a mineral’s streak does not match the mineral’s external color For example, one way to tell the difference between pyrite (Fool’s gold) and real gold is by streak. Pyrite leaves a greenish-black streak while real gold leaves a yellow streak.

Mineral Properties Color Luster Transparency Streak Cleavage & Fracture Crystalline Structure Texture Hardness The pattern of atoms will determine how a mineral will break A mineral that breaks relatively easily and evenly at angles is said to have cleavage Minerals that break with rough or jagged edges are said to have fracture

Mineral Properties Color Luster Transparency Streak Cleavage & Fracture Crystalline Structure Texture Hardness Mineral crystals occur in various shapes and sizes. The regular pattern of atoms, molecules or ions in a crystal. Atoms in a mineral are arranged in a systematic and repeating pattern

Mineral Properties Texture describes how a mineral feels to the touch. Talc has a soapy texture. Color Luster Transparency Streak Cleavage & Fracture Crystalline Structure Texture Hardness Texture describes how a mineral feels to the touch. Minerals can range anywhere between glassy feeling, rough feeling, greasy feeling, and even soapy feeling! Fluorite has a glassy texture.

Mineral Properties Color Luster Transparency Streak Cleavage & Fracture Crystalline Structure Texture Hardness Hardness is a measure of how easily a mineral can be scratched Geologists use Mohs Scale to give minerals their hardness ratings