To be able to identify these and other minerals, we need to look at the properties used to separate and distinguish these minerals.

Rarely is a mineral identified by a single property. Identifying Minerals Remember!: Rarely is a mineral identified by a single property. These properties need to be considered together to correctly identify a mineral.

color Color is the most easily observed mineral property and the least useful!

color Some exceptions to the color rule would be cinnabar, which is always red, and malachite, which is green.

Many minerals have a similar color.

color Many minerals can turn colors due to impurities, or they can change colors in various circumstances.

color For example, pure quartz is colorless or white, impurities can make the mineral rose, purple or pink!

Quiz Break!

How many of the characteristics of minerals can you name? Discuss the following! How many of the characteristics of minerals can you name? Why isn’t color a very good property to identify most minerals?

Luster refers to the way a mineral shines in reflected light. Notice the difference between these two minerals?

luster The mineral on the left has a metallic luster, the one on the right, a nonmetallic luster.

luster There are several terms used to describe nonmetallic luster. Examples could be vitreous, like the quartz on the left, or pearly, like the gypsum on the right.

Other terms that might be used include greasy, dull, and earthy. Can you tell which of these has an earthy luster and which has a vitreous luster? Were you Right? Vitreous Earthy

streak Streak of a mineral is the color of its powder when rubbed on an unglazed white tile.

The streak is often not the same color as the mineral. A minerals color may vary, but the streak rarely will!

crystal shapes Crystal shape can be a useful property to identify minerals if the minerals have had the time and space to form crystals. Most mineral grains that are found in rocks, lack the room to grow.

Crystal Shape (or form) External expression of a mineral’s internal atomic structure Planar surfaces called crystal faces Angles between crystal faces are constant for any particular mineral Quartz Pyrite

cleavage The cleavage of a mineral is its tendency to split easily or to separate along flat surfaces. Cleavage can even be observed on tiny mineral grains making it a very useful property! Do NOT confuse cleavage planes with crystal faces! Crystal faces are just on the surface and may not repeat when the mineral is broken!

cleavage Mica is probably the best example as it splits into thin sheets. It is said to have one perfect cleavage.

Cleavage (1 direction): Example: mica

cleavage Feldspar splits readily in two directions, always at or near right angles.

Cleavage (2 directions): orthoclase amphibole

Calcite and galena cleave in three directions. cleavage Calcite and galena cleave in three directions. They are said to have three good cleavages.

Cleavage (3 directions): halite calcite

Cleavage (4 directions): fluorite

Not all minerals show cleavage. Those that don’t break along cleavage surfaces are said to have fracture.

Minerals that have some weak bonds will show cleavage Fracture Minerals that have some weak bonds will show cleavage Minerals,like quartz, that have very strong bonds show fracture

Quiz Break!

There are four common minerals, how many can you name? Discuss the following! There are four common minerals, how many can you name? Of the four common minerals, which one makes up over 60% of the Earth’s crust?

The hardness of a mineral is its resistance to being scratched. Diamond is the hardest of all minerals, and talc is the softest.

Friedrich Mohs devised a hardness scale. In this scale, ten wellknown minerals are given numbers from one to ten. Lets take a look at the ten minerals used and some of the simple tests.

Hardness Talc (left) is the softest and has a hardness of 1. A soft pencil lead will scratch talc. Gypsum is a bit harder and has a hardness of 2. A fingernail scratches gypsum.

Hardness Calcite (left) has a hardness of 3 and a copper penny just scratches it. Fluorite has a hardness of 4 and it can be scratched by an iron or brass nail.

Feldspar has a hardness of 6 and it will scratch a window glass. Apatite (left) has a hardness of 5 and can be scratched by a steel knife blade. Feldspar has a hardness of 6 and it will scratch a window glass.

Topaz has a hardness of 8 and will scratch quartz. Quartz (left), with a hardness of 7, is the hardest of the common minerals. It easily scratches hard glass and steel. Topaz has a hardness of 8 and will scratch quartz.

Corundum (left) has a hardness of 9. Corundum will scratch topaz. Diamond with its hardness of 10 can easily scratch the rest of the minerals.

Quiz Break!

Does this mineral show cleavage or fracture? Discuss the following! Does this mineral show cleavage or fracture? Of the four most common minerals, which is the highest hardness?

Pure gold can have a specific gravity as high as 19.3! Specific gravity tells you how many times as dense as water the mineral is. Pure gold can have a specific gravity as high as 19.3!

acid test Calcite is calcium carbonate, CaCO3. If a drop of weak hydrochloric acid is placed on calcite, the acid bubbles as carbon dioxide is released.

Other Special Properties Magnetic Malleable Radioactive Flourescence Taste

Can you think of a mineral that might be shaped or hammered? Malleable or Ductile Minerals that can be hammered thin or shaped are said to show these properties. Can you think of a mineral that might be shaped or hammered?

Gold would be a perfect example!

Magnetic Some minerals that contain Iron, are magnetic and can be picked up by a magnet.

This is the state of glowing while under a ultraviolet light. Fluorescence This is the state of glowing while under a ultraviolet light. Some minerals even glow once the light is turned off!

Some minerals, such as this uraninite, are radioactive. They give off subatomic particles that will activate a Geiger counter.

Halite (rock salt) can be identified by its taste. This practice is not recommended!

Chemistry and Mineral Properties-Hardness The stronger the bond, the Harder the mineral Covalent bonds are the usually the hardest minerals; van der Waals are the softest minerals 3D structures are harder than 2D structures Minerals with water in their structure are generally softer Larger the cation & anion Longer the bond, the softer the mineral

Chemistry and Mineral Properties-Density The harder the mineral, the more dense it usually is

Chemistry and Mineral Properties-Color The most common cause of color in minerals is interaction with light outer-shell electrons. Minerals of Hard cations (no outer shell electrons) have no color and are white or clear Minerals of Soft cations (a few outer-shell electrons) commonly have colors unique to the cation. (Hematite: Fe+3 is red)

Color of Minerals

Uses of Minerals

2.9 Million Pounds! Lead: 777 lbs Iron: 14, 530 lbs Zinc: 544 lbs Clays: 12,121 lbs Copper: 932 lbs Salt: 31,779 lbs Aluminum: 4,040 lbs Stone, sand, & gravel: 1.11 million lbs

Common uses include: http://www.mii.org/commonminerals.php Aluminum--packaging, transport, building Beryllium--gemstones, fluorescent lights Copper--electric cables, wires, switches Feldspar--glass and ceramics Iron--buildings, automobiles, magnets Calcite--toothpaste, construction http://www.mii.org/commonminerals.php

Birthstones January: Garnet February: Amethyst March: Aquamarine April: Diamond May: Emerald June: Pearl & Alexandrite July: Ruby August: Peridot September: Saphhire October: Tourmaline & Opal November: Topaz and Citrine December: Tanzanite, Zircon, & Turquoise

Fireworks Red: Strontrium Orange: mixture of Strontrium and Sodium Americans use 30,000 tons of fireworks per year! Lets look at the minerals that make up the colors of fireworks Red: Strontrium Orange: mixture of Strontrium and Sodium Yellow: sodium Gold sparks: iron fillings and charcoal Bright Flashes: Aluminum Powder Green: Barium Blues: Copper Lavender: mixture of copper and strontium Silver/White: mixture of titanium, zirconium, and magnesium Silver/white flashes: Magnalium

Time for some research! For homework, you will be doing the Mineral Mania Project Use the following websites to get the information not covered in class: http://www.minsocam.org/MSA/K12/uses/uses.html for minerals in the home http://www.rocksandminerals.com/uses.htm for uses of common minerals Ask me if you need print outs of the website!