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Minerals Natural Solid Inorganic Definite chemical composition Crystal structure due to internal arrangement of atoms

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Presentation on theme: "Minerals Natural Solid Inorganic Definite chemical composition Crystal structure due to internal arrangement of atoms"— Presentation transcript:

1 Minerals Natural Solid Inorganic Definite chemical composition Crystal structure due to internal arrangement of atoms

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3 General Facts about Minerals Between 2 - 3,000 have been identified A few are “native elements” -- made of only one element, such as sulfur, gold. copper, and graphite (carbon) Most are compounds, especially the silicate group (Si, O). Other important groups are oxides, carbonates, and sulfides.

4 Less than a dozen are common in most rocks Quartz Feldspar (group) Muscovite (white mica) Biotite (black mica) Calcite Pyroxene Olivine Amphibole (group) Magnetite, limonite, and other iron oxides Pyrite

5 Common uses include: Aluminum--packaging, transport, building Beryllium--gemstones, fluorescent lights Copper--electric cables, wires, switches Feldspar--glass and ceramics Iron--buildings, automobiles, magnets Calcite--toothpaste, construction

6 Minerals are identified by their key characteristics hardness crystal shape (form) luster color streak cleavage/fracture density (specific gravity) special properties -- reaction to acid -- fluorescence -- salty taste -- magnetism

7 1. Mineral Hardness Ability to scratch another mineral Mohs scale from 1 (talc) to 10 (diamond) Quartz (most common mineral and most dust particles) is 7

8 2. Crystal Shape (Form) External structure due to internal arrangement of the atoms Six basic groups of shapes, with about three dozen variations

9 3. Luster Describes how light reflects off the surface Main categories are “metallic” and “non- metallic” Non-metallic includes “dull,” glassy,” waxy,” “pearly,” and others ulfides/pyrite/pyrite2.htm

10 4. Color results from ability to absorb some wavelengths and reflect others some minerals have characteristics colors others vary due to chemical differences or impurities (atoms mixed inside the main elements)

11 5. Streak Color of the powder when rubbed on a “streak plate” (unglazed porcelain) May be same as hand-specimen or different Some paint is based on powdered minerals (streaks).

12 6. Mineral cleavage/fracture Some minerals split along flat surfaces when struck hard--this is called mineral cleavage Other minerals break unevenly along rough or curved surfaces--this is called fracture A few minerals have both cleavage and fracture

13 7. Density (Specific Gravity) All minerals have density (mass / volume), but some are very dense Examples include galena, magnetite, and gold Specific Gravity is the density of the mineral compared with density of water

14 Special Characteristics-- 1. the “Acid Test” Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas)

15 Special Characteristics-- 2. Fluorescence Some minerals will glow when placed under short-wave or long-wave ultraviolet rays Franklin and Ogdensburg NJ are famous for their fluorescent minerals

16 Special Characteristics-- 3. Salty Taste DO NOT TASTE MOST MINERALS! Halite is the exception-- it will taste salty

17 Special Characteristics-- 4. Magnetism Many iron minerals will produce an invisible magnetic force field “Lodestone” was used by Vikings more than 1,000 years ago as compasses

18 Mineral Identification Key I. Mineral has a colored streak  A. Mineral has a black or grayish streak.  B. Mineral leaves a brown or reddish-brown streak.  C. Mineral leaves either a blue or a green streak. II. Mineral does not leave a colored mark on streak plate, but leaves a white streak or scratches the streak plate.  A. Mineral will scratch glass  B. Mineral will not scratch glass but will scratch a penny.  C. Mineral will not scratch a penny, and cannot be scratched by your fingernail.  D. Mineral can be scratched by your fingernail.

19 Mineral Identification Key

20 I.Mineral has a colored streak. A. Mineral has a black or gray streak. 1. Has a metallic gold appearance. It leaves a black Streak.= Pyrite 2.Leaves a “lead gray” streak, and has a bright silver metallic luster. It’s heavy.= Galena

21 I. A. Mineral has a black or grayish streak. 3. Will write on paper (easily), and feels greasy. = Graphite 4. Is “magnetic” = Magnetite

22 I. B. Mineral leaves a brown or reddish- brown streak. 1. Has brown circles on it’s surface. = Bauxite 2. Has a bumpy surface. = Hematite

23 I. C. Mineral leaves either a blue or a green streak. 1. Green streak. = Malachite (Often appears with Azurite.) 2. Blue streak.=Azurite (Often appears with Malachite)

24 Mineral Identification Key

25 II. No colored mark on the streak plate, but leaves a white streak or scratches streak plate. 1. Clear or translucent. Has a hardness of 7.= Quartz  If Pink = Rose Quartz.  If Dark = Smoky Quartz. II. A. Will scratch glass. Hardness 6-10

26 6-10 II. A. Mineral will scratch glass Hardness: Is orange and white in color. It has a hardness of 6. Distinct 90 ̊ cleavage. = Feldspar 3. Mineral is reddish- purple in color and has a hardness of 9. = Corondum

27 4-5 II. B. Mineral will not scratch glass, but will scratch a penny. Hardness: Mineral is light green in color and has a hardness of 5. = Apatite 5. Translucent and writing appears double when looking through it. = Calcite

28 II. B. Mineral will not scratch glass, but will scratch a penny. 4. Transparent to translucent. Mineral varies in color. It is often purple. Often shows good cleavage. = Fluorite

29 2-3 II. C. Mineral will not scratch a penny, and cannot be scratched by your fingernail. Hardness: Mineral has cubic cleavage and tastes salty. = Halite 2.Is in think flat sheets and peels off in layers. In Mica Family. -Dark Mica=Biotite -Light Mica=Muscovite

30 1-2 II. D. Mineral can be scratched by your fingernail. Hardness: Mineral feels soapy and has a hardness of one. = Talc 2. Transparent or translucent and has good cleavage. Mineral has silky luster and hardness of two. = Gypsum

31 Useful Web Sites mineralindex.htm


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