Minerals Examine the group of minerals: Minerals are the building blocks of rocks. Minerals are defined as any naturally occurring inorganic solids that possess an orderly internal structure and a definite chemical composition. Each of the Earth’s 4000 minerals is a unique substance. The uniqueness is determined by its chemical composition and internal structure of atoms. The basic building blocks of minerals are the chemical elements. Of the 110 + known elements, only 92 are naturally occurring. A few minerals such as gold, silver, sulfur are made entirely of one element. Most minerals are made of a combination of two or more elements, joined to form a chemically stable compound. The atoms of elements combine with each other to form a variety of complex compounds. A compound consists of two or more elements bonded together in definite proportions. Protons, Neutrons and Electrons Atoms of Elements  Molecules of Compounds  Some of these are minerals

X X X In order to be called a mineral it must meet 5 characteristics. (1) It must be a solid. It must be inorganic, meaning it was never alive. (3) It must possess an orderly internal structure, meaning its atoms must be arranged in a definite pattern (crystals or crystalline). X X X The properties of a chemical compound are very different from the properties of the elements composing it. Elements join together to form a mineral that is usually a compound. The elements making up the mineral lose their physical properties and the mineral has its own specific properties. A rock is not a compound but a mixture of minerals, each mineral keeps its own distinctive properties. A mineral is a naturally occurring crystalline solid with a definite, but not fixed, chemical composition and characteristic crystal structure.

Let’s learn more about crystals Crystals with Tim and Moby

Crystal lattice Formed when atoms join together in a repeating pattern. This is what gives the minerals their unique shapes

There are 7 main types of crystals There are 7 main types of crystals. The crystal structure of a mineral is sometimes obvious but sometimes can only be determined by using x-rays.

X CaAl2Si2O8 It must be formed naturally. (5) It must have a definite chemical composition. X CaAl2Si2O8

Use the characteristics of a mineral to complete the Table. √ Not a solid. Solid & crystalline. √ √ Not naturally occurring. √ Naturally occurring & crystalline. √ Organic. √ Not a solid. √ Solid & crystalline. √ Made by man.

How to Identify Minerals:

Do Now: You have 4 samples 1. Salt 2. Rock Clay Sugar For each one of the samples, do the following: Decide if the sample is a mineral or not a mineral. What is your evidence or reason(s) for your decision.

1. Color – Minerals come in different colors or even no color.

Olivine

Sulfur

Potassium Feldspar

Talc Gypsum Calcite Quartz Why do you think it is not good to only use color when trying to determine what a mineral is? Talc Gypsum Calcite Quartz Different minerals may be the same color.

These are all the mineral calcite. One mineral can come in many colors.

2. Streak Test– color of the powder left behind on streak plate (ceramic tile)

Some minerals have a streak that is not the same as the color of the mineral. Example: Pyrite – It has a brassy yellow color but its streak is green-black.

Pyrite with its green-black streak. Hematite with its red-brown streak.

Metallic- looks like metal. Non-Metallic- doesn’t look like metal. 3. Luster – how light reflects off the mineral. There are two main types of luster: Metallic- looks like metal. Non-Metallic- doesn’t look like metal.

Graphite has a metallic luster. (silver – gray in color.) Quartz has a non-metallic luster.

Moh’s Hardness Scale – resistance to being scratched Moh’s Hardness Scale – resistance to being scratched. Hardness depends on how tightly packed the molecules are in the mineral.

This mineral will be soft due to the loose arrangement of the molecules

This mineral will be hard due to the tight arrangement of the molecules

Minerals are rated on a scale of 1-10 Minerals are rated on a scale of 1-10. Minerals with a hardness of 1 would be very soft and minerals with a hardness of 10 are very hard. Minerals with a higher number can scratch a mineral with a lower number.

Moh’s Scale of Hardness The scale is from 1-10 Diamond is the hardest mineral

Diamonds with a hardness of 10 can scratch corundum (rubies) with a hardness of 9.

5. Cleavage vs. fracture – how the mineral breaks apart

If the mineral has Cleavage: Tendency of a mineral to split along one or more smooth, flat surfaces, or planes. The mineral will usually have flat sides.

If the mineral has fracture: Broken pieces are jagged and irregular. Rough or uneven sides. There is no pattern.

There is a check in the column marked cleavage if the mineral has cleavage and a check under fracture if the mineral has fracture.

Mica Muscovite Biotite Phlogopite Lepidolite

Pyrite (Fools gold) Gold

Cleavage of Feldspar Cleaves at 90o angles

Galena Cleavage is in 3 directions at 90o

Fracture of Quartz

6. Hydrochloric (HCl) Acid test on Calcite Fizzes on contact

The only mineral in a solid rock form, that has this characteristic is calcite.

What are minerals composed of? Made up of elements Most minerals (60%) are SILICATES (SiO2)– contain both oxygen and silicon

The mineral’s composition is written in symbol form – names of elements are found at the bottom of the chart

Composition of Earth’s Crust

R.T. pg. 11

Silicon-Oxygen Tetrahedron This is the basic structural unit of silicate minerals Contains 4 large oxygen ions at corners and 1 small silicon ion in center

Silicon Oxygen Tetrahedron Notice the Pyramid shape of the atoms

Silicon Oxygen Tetrahedron

How minerals look on the outside is directly related to the internal arrangement of atoms.

Magnetite

Halite Salt

Graphite

Mineral Crystals under Polarizers

Properties of Common Minerals (R.T. pg. 16) Q: Which minerals have metallic luster? A: Graphite, Galena, Magnetite, Pyrite Q: Which minerals have fracture? A: Magnetite, Pyrite, Hematite, Sulfur, Olivine, Quartz, Garnet Q: Which minerals have a hardness of 7? A: Quartz, Garnet Q: Which mineral will attract a magnet? A: Magnetite Q: Which mineral tastes salty? A: Halite

Do you remember what determines a minerals basic properties such as its hardness and cleavage??????

The internal arrangement of the atoms!!!