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Presentation on theme: "MINERALS."— Presentation transcript:


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)
Inorganic Crystalline Solid (interlocked pattern of molecules) Definite chemical structure which give it unique physical properties. Ex. Diamonds

4 Minerals vs. Rocks There 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 contains Protons- positive electrical charges Neutrons - no charge Shells which surround the nucleus and contain Electrons - negative electrical charges The 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 Calcium 1 Carbon CaCO3 3 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 Minerals The 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 minerals May contain one or more other elements Silicates make up 96% of the Earth’s crust.

11 Silicate Mineral Groups
Feldspars – form depending on which metal combines with the Si + O atoms Two common types of feldspars: Orthoclase (K, Al) Plagioclase (Ca, Na) Most plentiful mineral group Quartz – composed ONLY of Si + O atoms ( NO other elements )

12 Silicate Minerals Biotite Quartz Muscovite Plagioclase Feldspar

13 Non-Silicate Minerals
Major groups: *Contain no Silicon Oxides (metal + O) Ex. Hematite, magnetite Sulfides (metal + S) Ex. Pyrite “fool’s gold,” galena Sulfates (S +O) Ex. Gypsum [plaster] Halides Ex. Halites [salt] "Native" elements (don’t combine with any other elements) Ex. Gold, silver, carbon, copper Carbonates (C + O) Ex. limestone, marble Non-Silicates make up 4% of the Earth’s crust.

14 Non-Silicate Minerals
Pyrite Hematite Halite (salt)

15 Non-Silicate Minerals
Gold Flourite Galena

16 Mineral Properties Minerals 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 shine Color Streak –mineral’s color in powdered form Hardness –Mohs hardness scale/scratch resistance of one mineral against another Cleavage –how it breaks along preferred planes Fracture –no preferred plane (no flat surface) Specific gravity -describes the density of the mineral Taste, Smell, Fluorescence etc.

17 Identifying Minerals Color – can help with mineral identification.
Color of the mineral Color of the streak on a porcelain plate Example = Hematite is gray in color and has a red streak

18 Identifying Minerals Luster – shiny or dull
Luster - the way a mineral reflects light Look for luster on a fresh surface. The three major types of luster are metallic, glassy (vitreous) and dull.

19 Cleavage – how mineral breaks
Name Plane =Basal 1 =Prismatic 2 3 =Cubic =Rhombo- hedral 3

20 (a) cubic (b) 12-sided (c) octahedral (d) hexagonal

21 Identifying Minerals Most minerals (except metals) have one or more cleavage planes that also help in determining their identity. Cleavage Plane – A region where a rock cleanly splits Occur in areas of weak bonds between atoms and molecules. Mica has 1 cleavage plane Halite has 3 cleavage planes

22 Mohs hardness scale 1. Talc 7. Quartz 2. Gypsum/fingernail 8. Topaz
3. Calcite/penny Corundum 4. Fluorite Diamond 5. Apatite 6. Potassium Feldspar/steel nail Scratch one mineral against another to see how resistant it is. 22

23 Material Mohs hardness scale Streak plate ~7 Glass plate Nail ~4 Copper/Penny ~3 Fingernail ~2

24 Mineral Identification
Common items to test for hardness A fingernail (2.5) will scratch gypsum and be scratched by calcite A penny (3) is scratched by fluorite Glass (5.5- 6) scratches apatite and is scratched by orthoclase (a feldspar)

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