Ore Mineralogy (EMR 331) - kau4) Native ore minerals.pdf · Uses of Gold Gold and its ally are...
Transcript of Ore Mineralogy (EMR 331) - kau4) Native ore minerals.pdf · Uses of Gold Gold and its ally are...
Ore Mineralogy (EMR 331)
Native Ore Minerals
Metals, Metals, Metals, ……….
Native Elements
• Metals – Gold, Silver, Copper, Platinum, Palladium, Osmium, Iridium, Iron, Fe-nickel
• Semi-metals – Arsenic, Bismuth, Antimony
• Non-metals – Sulfur, Diamond, Graphite
Atomic
structure of
native metals
Native Metals• metallic bonding
• dense, cubic close packing
• properties: soft, malleable, ductile, sectile, good heat and electrical
conductors
• variable melting points: low-Au, Ag, Cu; high-PGEs
AuAu AgAg CuCu PtPt
Gold
Heat, moisture, oxygen, and most corrosive agents have very little
chemical effect on gold, making it well-suited for use
in coins and jewelry.
The History Says
Gold is mentioned several times in the Old Testament. The south-east corner of
the Black Sea was famed for its gold. Exploitation is said to date from the time of
Midas, and this gold was important in the establishment of what is probably the
world's earliest coinage in Lydia between 643 and 630 BC.
The Present Scenario
The gold isotope Au-198, is used in some cancer treatments and for treating other
diseases.
Gold is a metallic element. Its atomic number is 79. It is soft, shiny, yellow, dense,
malleable and ductile. It does not react with most chemicals but is attacked by
chlorine, fluorine and aqua regia. This metal occurs in the form of nuggets or
grains in rocks. It is also found in alluvial deposits.
Gold is measured by troy weight and by grams. If alloyed with other metals, a
term 'carat' or 'karat' is used to indicate the amount of gold present. Pure gold is
24 carats.
Physical Properties of Gold
(25 ºC) 25.418 J/(mol-K)Heat capacity
324 kJ/molHeat of vaporization
12.55 kJ/molHeat of fusion
3129K (2856°C, 5173°F) Boiling point
1337.33 K (1064.18°C, 1947.52°F)Melting point
17..31 g/cm3Liquid density at melting point
19..3 g/cm3Density (near room temperature)
SolidPhase
Characteristics of Gold
Gold is yellow in color but can also occur in black or ruby when it is finely
divided. The colloidal solutions are intensely colored and are often purple. Gold's
plasmon frequency, lying in visible range, results in colors. It absorbs blue light
and causes the red and yellow light to be reflected.
Gold is most malleable and ductile. One gram can be beaten into a sheet of one
square meter. It readily forms alloy with many other metals. With copper it yields
redder metal, blue with iron, silver produces green, aluminum-purple and
platinum-white. Native gold contains generally 8-10% silver.
Gold is a good conductor of both heat and electricity. It is not affected by air and
most regents. Heat, moisture, oxygen, and most of the corrosive agents have very
little chemical effect on gold. Halogens chemically alters gold and aqua regia
dissolves it.
Uses of Gold
Gold and its ally are often used in jewelry, coinage and a standard for monetary exchange in many
countries.
Due to its high electrical conductivity and resistance to corrosion, it is used as industrial metal.
It is made into thread and used in embroidery.
It performs a critical functions in computers, communications equipment, spacecraft, jet aircraft engines
and host of other products.
The resistance to oxidation property, it is used as a thin layers electroplated on the surface of electrical
connectors to make sure of good connection.
It is used in restorative dentistry.
Colloidal gold (a gold nanoparticle) is an intensely colored solution and is used as gold paint on ceramics
prior to firing.
Chlorauric acid is used in photography to tone silver image.
Gold(III) chloride is utilised as catalyst in organic chemistry.
It is used in awards.
It is used for protective coatings on many artificial satellites as it is a good reflector of infrared and visible
light.
The isotope of gold, Au-198 is used in some cancer treatments and for other diseases.
Gold flake is used in sweets and drinks.
White gold serves as the substitute for platinum.
Green gold is used in specialized jewelry.
World Gold Markets
London as the great clearing house
New York as the home of futures trading
Zurich as a physical turntable
Istanbul, Dubai, Singapore and Hong Kong as doorways to important consuming regions.
Tokyo where TOCOM sets the mood of Japan
Mumbai under India's liberalized gold regime
Major Gold Producing Countries
South Africa
United States
Australia
China
Canada
Russia
Indonesia
Peru
Uzbekistan
Papua New Guinea
Ghana
Brazil
Chile
Philippines
Mali
Mexico
Argentina
Kyrgyzstan
Zimbabwe
Colombia
Native Gold
Native
Silver
Native
Copper
Native gold crystallized in Chrysocholla
(gossan),Chile(0.75 inch x 1 inch)
Romanian Gold on Quartz
A simply amazing museum quality specimen that dates circa 1750-1800. It's loaded
with fine leaf Gold from top to bottom and every leaf displays dozens of well defined
trigons under magnification. From Verespatak, Romania. It measures 8 cm by 7 cm.
These mines have been mined for centuries and were mined by the Romans long ago.
Native gold (leaf-like)
from Rosia Montana (Verespatek)
Alba Co., Romania
5.3 x 3.1 x 2.2 cm
Silver Ag
Atomic No. - 47
Silver has been used for thousands of years for ornaments and utensils, for trade, and as
the basis for many monetary systems.
The History Says
Associated with the moon, as well as with the sea and various lunar goddesses, silver
was referred to by alchemists by the name luna. One of the alchemical symbols for
silver is a crescent moon with the open part on the left.
The Present Scenario
In India, foods can be found decorated with a thin layer of silver, known as 'Varak.'
Silver is found in the earth as native silver, a mineral. It has a bright, metallic
luster. When it is untarnished, it has a white color. Silver is usually found with a
various different elements forming variety of minerals and ores. In gold, lead,
zinc, and copper ores, it is found in a very small amounts, which is known as trace
amount.
As a mineral, it crystallizes in the cubic (isometric) system. In a very rare cases
silver forms crystals. Generally, found in thin sheets or as long wires and bundles
of wires. Silver is soft with a hardness on Mohs scale only at 2 to 3. It is malleable
and ductile.
The name 'silver' was named from the Old English (Anglo-Saxon) word 'seolfer.'
The word is also related to 'silber' in German and 'zilfer' in Dutch. Earlier it was
also called by a Latin name 'Luna.' It simply means 'moon,' because of its bright
luster. The symbol 'Ag' has been taken from the Latin word for silver,
'Argentum.'
Physical Properties of Silver
Ductile and MalleableTenacity
OpaqueTransparency
Silver-white to light gray. Streak shiny.Streak
MetallicLuster
6.9 - 12 (10.5 when pure)Specific Gravity
HacklyFracture
2.5 - 3Hardness
Silver-white on untarnished surface. Tarnishes dark
yellow to black.Color
NoneCleavage
Sources of Silver
Silver occur in lead, zinc, and copper ore deposits. Seventy-five percent of the resources
in the world are found in association with other metal ores. The remaining is found with
gold. The most important ore mineral is argentite, Ag2S (silver sulfide).
Significant world silver producing countries are the US, Mexico, Peru, Chile, and
Canada. In the US, Nevada is leads in silver producing. There it occurs as a by-product
of gold mining.
Uses of Silver
For thousand of years silver has been used for jewelry and all types of decorative items.
It is used in silverware.
Silver bromide and silver nitrate are used in photography.
Silver conducts electricity well, so it is used in electrical products.
It is used by dentists in amalgam fillings.
It is used in the production of bearings.
As untarnished silver is the best reflector of light, it was used in ancient times to make
mirrors.
Sterling silver, an alloy of other metal (usually copper), was used as currency in the
United States.
Swirling wire of native silver from Freiberg,
Germany (6.8 cm x 4.2 cm)
Electrum (above): a bright yellow grain, less than 100 microns
long, and big for Central Wales. This sample is from Eaglebrook
mine, and the electrum (Au:Ag = 60:40) occurs embedded in
galena, associated with the extremely rare mineral tucekite (buff)
and chalcopyrite (yellow). A little pyrite (high relief) is also
present .
Very well crystallized Electrum (Silver rich gold) on
quartz. The analysis gave 31.47% silver.
Location :Verespatak (now Rosia Montana),
Transylvania, Romania.
Scale : 2.8 cm x 3.4 cm.
Lydian electrum trite, second major variety 4.74g, 12x11x4 mm), Sardis,
Lydia, Asia Minor (present-day Turkey), c. 600-560 BC. This is the second main
variety of Lydian trites, later, slightly more refined in style, and considerably
more common than the first. The sunburst above the lion's eye typically has more
rays, and the hatches making up the lion's mane point downward instead of
upward. It likely consists of about 54 percent gold, 44 percent silver, 2 percent
copper, plus trace elements. (Photo of this coin courtesy of Electrum USA Ltd).
Carthage electrum coin,
ca. 250 BC .British Museum .
Native Nickel in
Fe meteorites
Native Platinum
Native Non-metalsSulfurSulfur DiamondDiamond GraphiteGraphite
SS88 ring molecules ring molecules
bonded by weakbonded by weak
van van derder WaalsWaals
forcesforces
CC66 ring molecules ring molecules
bonded by weakbonded by weak
van van derder WaalsWaals
forces; good forces; good
electrical electrical
conductivityconductivity
StrongStrong
CovalentCovalent
BondsBonds
Synthetic (industrial) DiamondsSynthetic (industrial) Diamonds
Native Element OccurrencesGold Gold –– Hydrothermal fluids related to Hydrothermal fluids related to magmatismmagmatism; commonly occurs ; commonly occurs
in veins quartz and pyrite; may form in veins quartz and pyrite; may form detritaldetrital grains to produce placer grains to produce placer
deposits; Rarely occurs alloyed with other elements.deposits; Rarely occurs alloyed with other elements.
Silver Silver –– Hydrothermal ore deposits rich in sulfide, Hydrothermal ore deposits rich in sulfide, arsenidesarsenides, and , and
bismithidesbismithides; also commonly associated native copper.; also commonly associated native copper.
CopperCopper –– SulfideSulfide--poor hydrothermal ore deposits or secondary poor hydrothermal ore deposits or secondary
oxidation of Cuoxidation of Cu--sulfide minerals; most abundant occurrence is the sulfide minerals; most abundant occurrence is the
native copper deposits of the Keweenawan Peninsula of Upper native copper deposits of the Keweenawan Peninsula of Upper
Michigan where it occurs in lava flows and interflow conglomeratMichigan where it occurs in lava flows and interflow conglomerates. es.
PlatinumPlatinum –– Occurs as primary deposits in mafic intrusions and as Occurs as primary deposits in mafic intrusions and as
secondary placer deposits.secondary placer deposits.
DiamondDiamond –– Occurs in mantleOccurs in mantle--derived derived kimberlitekimberlite pipes with other high pipes with other high
temperature/high pressure mineralstemperature/high pressure minerals
SulfurSulfur –– Precipitates near volcanic vents from volcanic gasses and Precipitates near volcanic vents from volcanic gasses and
secondarily by oxidation of sulfide minerals. secondarily by oxidation of sulfide minerals.