Minerals

1. Minerals

2. Table of Contents • Minerals • Mineral Identification • Uses of Minerals • Journals

3. Minerals Chapter 17 Section 1

4. What is a mineral? • Minerals are inorganic, solid materials and an orderly arrangement of atoms. found in nature. • Inorganic means they usually are not formed by plants or animals. • Each mineral has unique characteristics you can use to identify it. • About 4,000 different minerals are found on Earth, but they all share four major characteristics.

5. Mineral Characteristics • All minerals are formed by natural processes. • These are processes that occur on or inside Earth with no input from humans. • Minerals are inorganic. • This means that they aren’t made by life processes. • Every mineral is an element or compound with a definite chemical composition. • Minerals are crystalline solids. • All solids have a definite volume and shape. • Only a solid can be a mineral, but not all solids are minerals.

6. Is it a Mineral? You can tell whether an object is a mineral by asking four questions. • Is it a nonliving material? • Is it a solid? • Does it have a crystalline structure? • Is it formed in nature?

7. How do minerals form? • Minerals form in several ways. • One way is from melted rock material inside Earth called magma. • Evaporation can form minerals. • A process called precipitation can form minerals, too. • Water can hold only so much dissolved material. Any extra separates and falls out as a solid.

8. Structure of Minerals • The word crystalline means that atoms are arranged in a pattern that is repeated over and over again. • 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.

9. Crystals • Not all mineral crystals have smooth surfaces and regular shapes. • There are six major crystal systems, which classify minerals according to their crystal structures.

10. Crystals from Magma • Hot melted 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.

11. 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. • When magma cools rapidly, the crystals that form will be small.

12. Crystals From Solutions • Crystals also can form from minerals dissolved in water and the water evaporates. • Minerals can form from a solution without the need for evaporation if too much of a substance is dissolved in water.

13. Earth’s Minerals • Ninety elements occur naturally in Earth’s crust. Approximately 98 percent (by weight) of the crust is made of only eight of these elements.

14. Mineral Groups • Minerals are divided into two groups based on their chemical composition. • Silicate minerals are minerals that contain a combination of silicon, oxygen, and one or more metals. • Most of the common rock-forming minerals belong to a group called the silicates. • These two elements alone combine to form the basic building blocks of most of the minerals in Earth’s crust and mantle. • Non-silicate minerals are minerals that do not contain compounds of silicon and oxygen.

15. Mineral Identification Chapter 17 Section 2

16. Properties of Minerals • Each mineral has a set of physical properties that can be used to identify it. • Pattern of atoms (crystals) • Cleavage or fracture • Color • Streak • Luster • Hardness • Specific Gravity

17. Crystals • The atoms making up the mineral are arranged in a repeating pattern. • Solid materials that have such a pattern of atoms are called crystals.

18. Cleavage and Fracture • The way a mineral breaks is another clue to its identity. • Minerals that split into pieces with smooth, regular planes that reflect light have cleavage • Not all minerals have cleavage. • Minerals that break into pieces with jagged or rough edges have fracture.

19. Color • Sometimes a mineral’s color can help you figure out what it is. But color also can fool you. • The common mineral pyrite has a shiny, gold color similar to real gold. • Because of this, pyrite also is called fool’s gold. • Minerals display a wide variety of colors, and often the same mineral can be found in many different colors. • Because of this, color is usually not the best way to identify a mineral.

20. Streak • Scraping a mineral sample across an unglazed, white porcelain tile, called a streak plate, produces a streak of color. • The streak is not necessarily the same color as the mineral itself. • The streak of powdered mineral is more useful for identification than the mineral’s color.

21. Streak FYI • The streak test works only for minerals that are softer than the streak plate. WHY? • Some soft minerals will leave a streak even on paper. • The last time you used a pencil to write on paper, you left a streak of the mineral graphite.

22. Luster • Luster describes how light reflects from a mineral’s surface. • If it shines like a metal, the mineral has metallic luster. • Nonmetallic minerals can be described as having pearly, glassy, dull, or earthy luster. • Terms for nonmetallic luster include dull, pearly, silky, and glassy.

23. Hardness • A 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.

24. Hardness • In 1824, Friedrich Mohs developed a way to classify minerals by their hardness. • The Mohs scale classifies minerals from 1 (softest) to 10 (hardest). • You can determine hardness by trying to scratch one mineral with another to see which is harder.

25. Specific Gravity • Measuring specific gravity is another way you can identify minerals. • Specific gravity compares the weight of a mineral with the weight of an equal volume of water. • Pyrite—or fool’s gold—is about five times heavier than water. Pure gold is more than 19 times heavier than water. • Specific gravity is expressed as a number.

26. Density • Density is the measure of how much matter is in a given amount of space. • Density is a ratio of an object’s mass to its volume. • Different minerals have different densities.

27. Unique Properties • The mineral magnetite will attract a magnet. • The mineral calcite has two unusual properties. • It will fizz when it comes into contact with an acid like dilute HCl. • If you look through a clear calcite crystal, you will see a double image.

28. Mineral Making Rocks • Only a small number of the more than 4,000 minerals make up most rocks. • Most of the rock-forming minerals are silicates, which contain the elements silicon and oxygen. • More than half of the minerals in Earth’s crust are types of a silicate mineral called feldspar. • Another group of important rock-forming minerals are carbonates. • The carbonate mineral calcite makes up most of the common rock limestone.

29. Uses of Minerals Chapter 17 Section 3

30. Gems • Gems or gemstones are minerals that are rare and can be cut and polished, giving them a beautiful appearance. • Gemstones are highly valued for their beauty and rarity, than for their usefulness. • Important gemstones include diamond, sapphire, ruby, emerald, aquamarine, and topaz. • Most gems are special varieties of a particular mineral. • To be gem quality, most minerals must be clear with few or no blemishes or cracks.

31. The Making of a Gem • One reason why gems are so rare is that they are formed under special conditions. • Diamond, for instance, is a form of the element carbon. • Scientists suggest that diamond forms deep in Earth’s mantle. • It takes a certain kind of volcanic eruption to bring a diamond close to Earth’s surface, where miners can find it.

32. The Cullinan diamond, found in South Africa in 1905, was the largest uncut diamond ever discovered.The Cullinan diamond was cut into 9 main stones and 96 smaller ones. The largest of these is called the Cullinan 1 or Great Star of Africa, and it is now part of the British monarchy’s crown jewels. Another well-known diamond is the blue Hope diamond. The Hope diamond has gained a reputation for bringing its owner bad luck.The Hope diamond’s mass is 45.52 carats (about 9 g). Currently, it is displayed in the Smithsonian Institution in Washington, D.C. Gem Stories All gems are prized, but some are truly spectacular and have played an important role in history.

33. Useful Gems • Diamonds • Diamonds have a hardness of 10 on Mohs scale. They can scratch almost any material—a property that makes them useful as industrial abrasives and cutting tools. • Quartz • Quartz crystals are used in electronics and as timepieces. • Rubies • Rubies are used to produce specific types of laser light. • Most industrial diamonds and other gems are synthetic, which means that humans make them.

34. Ores • A mineral is called an ore if it contains enough of a useful substance that it can be sold for a profit. • Ores of these useful metals must be extracted from Earth in a process called mining. • Iron used to make steel comes from the mineral hematite • Lead for batteries is produced from galena, • Magnesium used in vitamins comes from dolomite.

35. Ore Processing • After an ore has been mined, it must be processed to extract the desired mineral or element. • Smelting melts the ore and then separates and removes most of the unwanted materials. • After this smelting process, it can be refined, which means that it is purified.

36. Useful Elements in Minerals • Metallic minerals are good conductors of heat and electricity. • Nonmetallic Minerals are good insulators of electricity. • Iron, used in everything from frying pans to steel for ships, is obtained hematite. • Lead for batteries is produced from galena • Magnesium used in vitamins comes from dolomite. • Aluminum is refined from bauxite.

37. Minerals Containing Titanium • Under certain conditions, metallic elements can dissolve in fluids then travel through weaknesses in rocks and form mineral deposits. • Mineral deposits left behind fill in the open spaces are called vein mineral deposits. • Titanium is a durable, lightweight, metallic element derived from minerals that contain this metal in their crystal structures. • Two minerals that are sources of the element titanium are ilmenite and rutile.

38. Uses of Titanium • Titanium is used in automobile body parts, such as connecting rods, valves, and suspension springs. • Wheelchairs used by people who want to race or play basketball often are made from titanium.

39. Problems with Mining • Mining gives us the minerals we need, but it may also create problems. • Mining can destroy or disturb the habitats of plants and animals. • One way to reduce the potential harmful effects of mining is to return the land to its original state after the mining is completed. • The process by which land used for mining is returned to its original sate or better is called reclamation. • Waste products from a mine may get into water sources, which pollutes surface water and ground water.