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.