2 What is a mineral?How do we differentiate a mineral from a piece of wood or a human?What is a rock?
3 Minerals What is a mineral? Naturally occurring (not man-made) InorganicCrystalline Solid (interlocked pattern of molecules)Definite chemical structure which give it unique physical properties.Ex. Diamonds
4 Minerals vs. RocksThere are nearly 4000 known minerals - but most rocks are formed by only a few dozen minerals.Rocks are aggregates (mixtures) of minerals. So minerals are the building blocks of rocks.Question :How do minerals come together to form a rock?
5 Composition and Structure of Minerals To understand how minerals form, we need to understand the characteristics of elements and atoms.Elements are the basic building blocks of minerals. There are over 100 known elements.Atoms are the smallest particle of matter that exhibits all the characteristics of an element.
6 Composition and Structure of Minerals Atoms are made up of:Nucleus, which containsProtons- positive electrical chargesNeutrons - no chargeShells which surround the nucleus and contain Electrons - negative electrical chargesThe mass (density) of an element depends on the number of protons and neutrons in the nucleus.
7 Combining Elements to Form Minerals Elements combine with each other to form a wide variety of minerals.The new mineral (compound) will have very different physical properties from the elements that combined to form it.Ex: 1 Calcium1 Carbon CaCO33 Oxygen
8 Combining Elements to Form Minerals Since rocks are mixtures (not chemical combinations) of minerals, minerals keep their physical properties within a rock.Question: Is it possible for two different minerals to have the same chemical composition?YES! Both diamond and graphite are made of carbon. The difference between these two minerals is the way in which the carbon atoms are arranged.
9 Rock Forming MineralsThe most common rock forming minerals are composed of 8 elements:Oxygen (O)Silicon (Si)Aluminum (Al)Calcium (Ca)Sodium (Na)Potassium (K)Iron (Fe) and Magnesium (Mg)There are just a few dozen minerals that we call the rock-forming minerals.
10 Silicate Minerals Silicate minerals: Contain both silicon (Si) and oxygen (O)The most common rock-forming mineralsMay contain one or more other elementsSilicates make up 96% of the Earth’s crust.
11 Silicate Mineral Groups Feldspars – form depending on which metal combines with the Si + O atomsTwo common types of feldspars:Orthoclase (K, Al)Plagioclase (Ca, Na)Most plentiful mineral groupQuartz – composed ONLY of Si + O atoms( NO other elements )
13 Non-Silicate Minerals Major groups: *Contain no SiliconOxides (metal + O) Ex. Hematite, magnetiteSulfides (metal + S) Ex. Pyrite “fool’s gold,” galenaSulfates (S +O) Ex. Gypsum [plaster]Halides Ex. Halites [salt]"Native" elements (don’t combine with any other elements) Ex. Gold, silver, carbon, copperCarbonates (C + O) Ex. limestone, marbleNon-Silicates make up 4% of the Earth’s crust.
16 Mineral PropertiesMinerals have lots of different properties that help us identify them:Crystal form -set of faces that have a definite geometric relationship to one another.Luster –metallic or nonmetallic shineColorStreak –mineral’s color in powdered formHardness –Mohs hardness scale/scratch resistance of one mineral against anotherCleavage –how it breaks along preferred planesFracture –no preferred plane (no flat surface)Specific gravity -describes the density of the mineralTaste, Smell, Fluorescence etc.
17 Identifying Minerals Color – can help with mineral identification. Color of the mineralColor of the streak on a porcelain plateExample = Hematite is gray in color and has a red streak
18 Identifying Minerals Luster – shiny or dull Luster - the way a mineral reflects lightLook for luster on a fresh surface.The three major types of luster aremetallic,glassy (vitreous)and dull.
19 Cleavage – how mineral breaks NamePlane=Basal1=Prismatic23=Cubic=Rhombo-hedral3
21 Identifying MineralsMost minerals (except metals) have one or more cleavage planes that also help in determining their identity.Cleavage Plane – A region where a rock cleanly splitsOccur in areas of weak bonds between atoms and molecules.Mica has 1 cleavage planeHalite has 3 cleavage planes
22 Mohs hardness scale 1. Talc 7. Quartz 2. Gypsum/fingernail 8. Topaz 3. Calcite/penny Corundum4. Fluorite Diamond5. Apatite6. Potassium Feldspar/steel nailScratch one mineral against another to see how resistant it is.22
24 Mineral Identification Common items to test for hardnessA fingernail (2.5) will scratch gypsum and be scratched by calciteA penny (3) is scratched by fluoriteGlass (5.5- 6) scratches apatite and is scratched by orthoclase (a feldspar)