2Objective3 Define chemical and physical properties of minerals to include luster, hardness, cleavage, fracture, streak, color, specific gravity, and special traits.
3Enduring Understanding Minerals are the building blocks of rocks.
4Mineral Identification With more than 3,000 minerals in Earth’s crust how does one go about identifying an unknown mineral?
5Mineral Identification Geologists rely on several simple tests that are based on a mineral’s physical and chemical properties. It is usually best to use a combination of tests rather than just one to identify minerals
6Mineral PropertiesColor is one of the most noticeable but least reliable characteristics
7Mineral Properties Quartz Sometimes caused by the presence of trace elements or compoundsQuartz
8Mineral PropertiesStreak is the color of the mineral when it is broken up into a powder and is a much more reliable identification method because it rarely changesBoth of these samples are hematite; both have a reddish-brown streak
9Mineral PropertiesStreak is easily determined by rubbing the mineral across an unglazed porcelain plate
10Mineral PropertiesStreak is used to distinguish pyrite from gold
11Mineral Properties Pyrite Gold Streak is used to distinguish pyrite from goldPyriteGold
12Mineral PropertiesLuster is the way a mineral reflects light from its surface and is caused by differences in mineral chemical compositions
13Mineral PropertiesEither metallic or nonmetallic (dull, pearly, waxy, silky)
14Mineral Properties Texture describes how a mineral feels to the touch Rough, smooth, ragged, greasy, soapy, glassy
15Mineral PropertiesHardness is a measure of how easily a mineral can be scratched and is determined by the arrangement of it’s atoms.
16Mineral PropertiesThe Mohs hardness scale is used to compare a sample to the hardness of ten known minerals
17Mineral PropertiesCleavage determines whether a mineral will split easily and evenly along one or more flat planes
18Mineral Properties Mica has perfect cleavage in one direction Halite has cubic cleavage (3 planes)
19Mineral PropertiesFracture means the mineral is tightly bonded and breaks with rough or jagged edgesQuartz has fracture
20Mineral PropertiesSpecific Gravity compares the weight of the mineral to an equal volume of water at 4 degrees C
21Mineral PropertiesSpecial Properties such as light reflection and reactions to acids are also useful tools
22Mineral PropertiesCalcite fizzles when in contact with HCl
23Mineral PropertiesCalcite also can cause double images
31Element or compound with a definite chemical composition
32Orderly arrangement of atoms; all minerals are crystalline solids
33Crystal—solid with atoms arranged in orderly, repeating patterns
34Some crystals form from magma, hot melted rock below the Earth’s surface.
35When magma cools slowly, crystals are large. When magma cools quickly, crystals are small.
36Crystals can form from solutions as water evaporates or if too much of a substance is dissolved in water.
37Mineral groups are defined by their composition. Silicates contain silicon, oxygen, and one or more other elements; they include most common rock-forming minerals.Silicon and oxygen are the two most abundant elements in Earth’s crust; they form the building blocks of many minerals.
38DISCUSSION QUESTION:What processes can cause crystals to form?
39DISCUSSION QUESTION:What processes can cause crystals to form?Crystals form from cooling magma, from evaporating solutions, and from solutions in which too much of a substance is dissolved.
40Mineral Identification Color and appearance are not enough to distinguish most minerals.
41Hardness is a measure of how easily a mineral can be scratched; the Moh’s scale compares mineral hardness.
42Talc - easily scratched by the fingernail Gypsum - just scratched by the fingernailCalcite - scratches and is scratched by a copper coinFluorite - not scratched by a copper coin and does not scratch glassApatite - just scratches glass and is easily scratched by a knifeOrthoclase - easily scratches glass and is just scratched by a fileQuartz - (amethyst, citrine, tiger's-eye, aventurine) not scratched by a fileTopaz - scratched only by corundum and diamondCorundum - (sapphires and rubies) scratched only by a diamondDiamond - scratched only by another diamond
53The way a mineral reflects light is its luster. Luster can be metallic or nonmetallicNonmetallic lusters include dull, pearly, silky, and glassy.
54Specific gravity is the relationship between a mineral’s density to the density of water. If the specific gravity is larger than one it will sink in water, if it is smaller than one it will float in water.
55Streak is the color of a mineral in powdered form, but the streak test is useful only for minerals softer than the streak plate.
56The way a mineral breaks can be a distinguishing characteristic. Minerals withcleavage breakalong smooth,flat surfaces.
57Minerals with fracture break with uneven, rough, or jagged surfaces.
58Some minerals have unique properties that involve light or magnetism.
59DISCUSSION QUESTION:What are five properties that could be examined to identify a mineral?
60DISCUSSION QUESTION:What are five properties that could be examined to identify a mineral?hardness, luster, specific gravity, streak, cleavage, and fracture
61Gems—rare and beautiful minerals that are highly prized The Cullinan diamondand the Hope diamondare famous historical gems.Gems have industrialapplications in abrasives,lasers, and electronics.
62Minerals can contain other useful elements. An ore is a mineral or rock containing a substance that can be mined at a profit.Elements must be refined, or purified, from ores.
63Some elements dissolve in fluids, travel through weaknesses in rocks, and in those weaknesses form mineral deposits called vein mineral deposits.
64Titanium is a useful element derived from the minerals ilmenite and rutile.
65Mica is an example of a mineral with the characteristic of cleavage, Mica is an example of a mineral with the characteristic of cleavage, because it can be separated into sheets.
66Graphite is one of the softest minerals and is used in pencils.
67Sulfur is a bright yellow mineral with Sulfur is a bright yellow mineral with the distinctive odor of spoiled eggs.