Minerals Essential Question: What are the physical characteristics used to distinguish between minerals & rocks? SWBAT: Explain how scientists use physical characteristics to identify and classify minerals and rocks.

What is a mineral? A mineral is a naturally occurring , inorganic solid with a specific chemical composition and an orderly arrangement of atoms (crystal structure).

Mineral Characteristics All minerals share the same 4 characteristics: Formed by natural process Minerals are inorganic (non-living) solid Every mineral is an element or compound with a definite chemical composition Minerals are crystalline solids with definite volume and shape (atom pattern)

Atom Patterns The word crystalline means that the atoms are arranged in a pattern that is repeated over and over again throughout the entire piece.

The structure of Minerals A crystal is a solid in which the atoms are arranged in orderly, repeating patterns. A crystal system is a group of crystals that have similar atomic arrangements and therefore similar external crystal shapes.

Crystals There are 6 major crystal systems, which classify minerals according to their crystal structures.

Crystals

Crystals from magma Molten rock material, called magma, cools when it reaches Earth’s surface, or even if it’s trapped below the surface. As magma cools, its atoms lose heat energy, move closer together, and begin to combine into compounds.

Crystals from magma Atoms of the different compounds arrange themselves into orderly, repeating patterns. The type and amount of elements present in magma partly determine which minerals will form. When magma cools slowly, the crystals that form are generally large enough to see with the unaided eye. (slow=large) When magma cools rapidly, the crystals that form will be small. (fast=small)

Crystals from solution Crystals also can form from minerals dissolved in water. When water evaporates, as in a dry climate, ions that are left behind can come together to form crystals.

Crystals from solution OR, if too much of a substance is dissolved in water, ions can come together and crystals of that substance can begin to form in the solution. Minerals can form from a solution in this way without the need for evaporation.

Mineral Compositions and Groups Ninety elements occur naturally in Earth’s crust. Approximately 98 percent (by weight) of the crust is made of of only eight of these elements.

Mineral Compositions and Groups Most of the common rock-forming minerals belong to a group called the silicates. Silicates (SIH luh kayts) are minerals that contain silicon (Si) and oxygen (O) and usually one or more other elements. These two elements alone combine to form the basic building blocks of most of the minerals in Earth’s crust and mantle.

Question 1 Which of these is a characteristic of minerals? A. crystalline solid B. formed by life processes C. indefinite chemical composition D. organic substances

Answer The answer is A. Minerals are crystalline solids.

Question 2 When magma cools rapidly, it forms __________. A. evaporites B. large crystals C. opals D. small crystals

Answer The answer is D. When magma cools rapidly, it forms small crystals that are difficult to see.

Question 3 Minerals that contain silicon and oxygen are __________. A. magma B. opals C. silicates D. solutions

Answer The answer is C. Silicates contain silicon and oxygen and usually one or more other elements.

Mineral Identification Physical Properties (there are 8) What are physical properties? 2 ways to classify Chemical – what it is made of Physical – what it does

1. Mineral Color Color and appearance are clues to identify minerals Some other properties to study include how hard a mineral is, how it breaks, and its color when crushed into a powder.

2. Hardness The measure of how easily a mineral can be scratched is its hardness Sometimes the concept of hardness is confused with whether or not a mineral will break. It is important to understand that even though a diamond is extremely hard, it can shatter if given a hard blow in the right direction along the crystal.

Mohs Scale In 1824, the Austrian scientist Friedrich Mohs developed a list of common minerals to compare their hardness. This list is called Mohs scale of hardness. If a streak plate is 7, what would happen if diamond was tested on it?

3. Luster Luster is the way a mineral reflects light. Luster can be either metallic or nonmetallic. There are subcategories of nonmetallic luster Minerals with a metallic luster shine like metal. http://video.about.com/geology/What-Are-Mineral-Lusters-.htm

Luster When a mineral does not shine like a metal, its luster is nonmetallic. Terms for nonmetallic luster include dull, pearly, silky, and glassy.

4. Streak Streak is the color of a mineral when it is in a powdered form. The streak test only works for minerals that are softer than the streak plate. Some minerals can leave a streak on paper. Can you think of a mineral that leaves a streak on paper?

Streak When a mineral is rubbed across a piece of unglazed porcelain tile, a streak of powdered mineral is left behind.

5. Cleavage or Fracture The way a mineral breaks is another clue to its identity Minerals that break along smooth, flat surfaces or planes have cleavage Minerals that break with uneven, rough, or jagged surfaces have fracture

Cleavage and Fracture Cleavage is determined partly by the arrangement of the mineral’s atoms. Quartz is a mineral with fracture. Some minerals have unique properties. Magnetite is attracted to magnets.

Specific Gravity Minerals also can be distinguished by comparing the weights of equal-sized samples. The specific gravity of a mineral is the ratio of its weight compared to the weight of an equal volume of water. Specific gravity is expressed as a number. Specific gravity of Nickel is 8.9 specific gravity

Question 1 The Mohs scale uses __________ to compare minerals. A. cleavage B. color C. hardness D. luster

Answer The answer is C. The Mohs scale, developed by Friedrich Mohs, rates the hardness of minerals from one to ten.

Question 2 Minerals that break easily along smooth, flat surfaces have __________. A. cleavage B. fracture C. luster D. streak

Answer The answer is A. Cleavage is determined partly by the arrangement of the mineral’s atoms. Minerals that break with uneven surfaces have fracture.

Question 3 Which of the following minerals will pick up iron filings? A. calcite B. feldspar C. lodestone D. quartz

Answer The answer is C. Lodestone is a variety of magnetite and is a natural magnet.

Uses of Minerals Gems What makes some minerals special? What properties do they have that make them so valuable?

Properties of Gems Gems or gemstones are highly prized minerals because the are rare and beautiful. Most gems are special varieties of a particular mineral They are clearer, brighter, or more colorful than common samples of the mineral Amethyst is a form of quartz that contains iron in its structure that makes it purple.

Properties of gems continued Sometimes a gem had a crystal structure that allows it to be cut and polished to a higher quality than that of a non-gem mineral.

Properties of gems

The Imperial State Crown Crown worn by monarch of the United Kingdom 2,868 diamonds 273 pearls 17 sapphires 11 emeralds 5 rubies

Important Gems All gems are prized, but some are truly spectacular and have played an important role in history. The Cullinan diamond, found in South Africa in 1905, was the largest uncut diamond ever discovered. It was but into 9 main stones and 96 smaller ones The largest, Cullinan 1 is 530.20 carats is also part of the British monarchy’s crown jewels.

Important Gems The blue Hope Diamond Gained a reputation for bringing its owner bad luck 45.52 carats On display at Smithsonian in Washington, D.C.

Useful Gems What is the hardness of diamonds on the Mohs scale? They can scratch almost any material – a property that makes them useful as industrial abrasives and cutting tools. Rubies are used to produce specific types of laser light Quartz crystals are used in electronics and as timepieces

Useful Elements in Minerals Ores Iron, used in everything from frying pans to ships, is obtained from its ore, hematite. A mineral or rock is an ore if: it contains a useful substance that can be mined at a profit

Ores Aluminum sometimes is refined, or purified, from th eore bauxite In the process of refining aluminum, aluminum oxide powder is separated from unwanted materials that are present in the original bauxite Then the aluminum oxide powder is converted to molten aluminum by a process called smelting

Vein Materials Under certain conditions, metallic elements can dissolve in fluids These fluids then travel through weaknesses in rocks and form mineral deposits Mineral deposits left behind that fill in the open spaces created by the weaknesses are called Vein mineral deposits

Minerals containing Titanium Titanium is a durable, lightweight, metallic element derived from minerals that contain this metal in their crystal structures To minerals that are sources of the element titanium are ilmenite and rutile Titanium is used in automobile body parts, such as connecting rods, valves, and suspension springs Wheelchairs for sports are often made from titanium

Question 1 Highly prized minerals called _______________ are rare and beautiful. Crystals Gems Grains ores

Answer The answer is B. Most gems are special varieties of a particular mineral. All minerals are crystalline solids, but not all of these are gems

Question 2 What must be true of a mineral or rock in order for it to be an ore?

Answer A mineral or rock is an ore of it contains a useful substance that can be mined at a profit.

Question 3 The ore bauxite can be processed to obtain ___________. Aluminum Iron Magnetite titanium

Answer The answer is A. Aluminum oxide is separated from the original bauxite, then converted to molten aluminum