Native Elements, Minerals Rocks - PowerPoint PPT Presentation

1 / 22
About This Presentation
Title:

Native Elements, Minerals Rocks

Description:

Only a few minerals occur as pure elements in the earth's crust. Gold Graphite Silver Sulfur Diamond Copper Platinum. Au C ... Almandine garnet coloured by iron ... – PowerPoint PPT presentation

Number of Views:607
Avg rating:3.0/5.0
Slides: 23
Provided by: ljbcW
Category:

less

Transcript and Presenter's Notes

Title: Native Elements, Minerals Rocks


1
Native Elements, Minerals Rocks Ores
  • Year 9
  • Geology Topic

2
Native Elements Only a few minerals occur as
pure elements in the earths crust.
  • Gold Graphite Silver Sulfur
    Diamond Copper Platinum
  • Au C Ag S
    C Cu Pt

3
Most are found as chemical compounds called
minerals
  • Beryl
  • Be Al Silicate
  • Quartz SiO2
    Calcite CaCO3

4
Rocks are mixtures of minerals and elements.
  • Lapis lazuli
    Unakite
  • Lazulite Boulder Opal
    quartz,feldspar
  • Calcite opal in cracks epidote
  • Pyrites of boulder

5
  • CHEMISTRY
  • An element contains only one type of atom
  • A compound contains two or more elements
    chemically combined
  • A mixture contains elements and or compounds that
    are not chemically combined
  • GEOLOGY
  • A Native Element contains only one type of atom
    and is found naturally on earth in its pure form.
  • A mineral contains two or more elements
    chemically combined
  • A rock contains a mixture of elements and
    compounds

6
ORES are rocks containing valuable minerals
  • Hematite Malachite Galena
  • Iron Ore Copper Lead

Gold in Quartz
7
ORES
  • Gold in W.A. is mined from tellurides, chlorites,
    quartz veins and in copper ores at Telfer
  • Gold nuggets are native elements.
  • Copper is found in cuprite, malachite and azurite
  • Native copper is rare
  • Diamond in W.A. is mined from volcanic plugs
    called Kimberlite pipes.
  • Iron ores consist of haemetite, magnetite, pyrite
    and limonite

Crystalline Haemetite is used to make jewellery
8
ORES
9
  • Only a few minerals are rock forming and most
    rock is made from a combination of the commonest
    of these such as feldspars, quartz, mica,
    olivine, calcite, pyroxene and amphiboles

10
Physical Properties of Minerals
  • COLOUR
  • HARDNESS
  • CLEAVAGE
  • SPECIFIC GRAVITY
  • STREAK
  • CRYSTAL FACES

11
Colour......................
Minerals tend to occur in a range of colours, and
colour patterns which help to identify them
  • Most minerals are coloured by a limited number of
    metals present as impurities.
  • The most common elements affecting colour are
  • chromium, iron, manganese, titanium and
    copper.
  •      

It is chromium which produces the intense red of
ruby and the brilliant green of emerald.
12
Quartz displays a profusion of colours, patterns
and optical effects unsurpassed by any other gem
  • colourless is rock
    crystal
  • purple quartz is amethyst
  • yellow is citrine
  • brown is smoky
    quartz
  • pink is rose quartz.
  • black is
    morion

13
Hardness................... -
  • Hardness depends upon the forces holding the
    atoms of the mineral together.
  • In 1812, a scientist, F. Moh devised a scale of
    hardness into which all minerals can be placed.
  • He selected ten minerals and arranged them in
    order so that any one mineral could be used to
    scratch only minerals which are less.
  • Diamond is the- hardest natural material, 140
    times harder than corundum.

14
Cleavage................
Distinct cleavage planes can be illustrated in
this box mica specimen


         
         
  • The manner in which a mineral splits is an aid to
    identification.
  • These planes are related to the lattice work of
    the mineral's atomic structure.

15
Streak
  • When minerals are scratched, the powder that is
    made by the scratch is called the streak.
  • Sometimes the colour of the streak can be used to
    identify the mineral.
  • Eg. Haemetite a black mineral has a red streak.
    No other black mineral has a red streak.

16
Specific Gravity...................
  •  
  • It was Archimedes who first worked out the
    principal of specific gravity or relative
    density. Specific gravity is defined as the ratio
    of the weight of a substance compared to that of
    an equal volume of water.
  • For example, a piece of galena (lead ore), with a
    specific gravity of 7.4 will feel much heavier
    than a piece of quartz of a similar size but with
    specific gravity of 2.65, reflecting the way the
    atoms are packed together.

17
Crystals
  • Crystals are minerals or elements that have
    been cooled slowly enough for crystals to have
    formed.
  • Such conditions occur most often in pegmatites
    or pipes.
  • Crystals can be classified by their shapes
    into seven groups.

18
Next slides are advanced or extension only .
19
Optical effects.
  • In diamond the 'fire' and sparkle is caused
    by dispersion as the gemstone acts like a prism.
  • The brilliant colours displayed by opal are
    caused by the light being scattered as it passes
    through planes of regularly spaced voids between
    the transparent silica spheres.  

20
Double Refraction .
  • Double refraction can be seen in a piece of
    Calcite.
  • Light separates into two rays which makes images
    seen through the crystal appear to be doubled.

21
Refraction....................
  • This is a measure of the mineral's ability to
    bend a beam of light. This ability is called
    refractive index.

Some gemstones can be identified by the spectral
colours they produce.
Ruby coloured by chromium
Almandine garnet coloured by iron
-Measuring refraction using an optical instrument
called a Refractometer.
22
What makes a mineral a Gemstone?
  • There are over two hundred recognised gemstones.
    Most are minerals and are cut from naturally
    occurring crystals.
  • To qualify as a gem, the specimen should be hard
    and tough to resist scratching and have beautiful
    clarity, colour or 'fire'. Value is based on
    rarity and rare quality.
Write a Comment
User Comments (0)
About PowerShow.com