42:271 Gems & Gemstones
Have intrigued people for the last 7,000 years
The first known were amethyst, rock crystal, amber, garnet, jade, jasper, coral, lapis lazuli, pearl, serpentine, emerald and turquoise
Were reserved for the wealthy as status symbols. Sealed documents had jewel-encrusted seals
Warning!
Imitations of gems with synthetic varieties are widespread today
You can easily be fooled by merchants
Up to the beginning of 19th cent. used as medicine against illnesses
Even today calcium tablets made out of powdered pearls are sold for medicinal purposes in Japan
Linked to astrology and allocated to zodiac as birthstones
Priests, bishops and kings wear them
Austrian crown recovered in Winnipeg in 2007!
A strange bank robbery on Empress St. in 1998 surprised police who conducted a world-wide search that ended in a St. James home where the Austrian jewel-encrusted broach – the Koechert Pearl Diamond of the Empress of Austria- was found. It had been stolen 9 years before
A very sophisticated robbery
Precious & semi-precious stones
In the past were only a few, now many
Most are minerals
Semi-precious are softer stones, no official list
Profusion of names, some created to boost sales, examples are tanzanite (blue zoisite) and tsavorite (green garnet)
Physical properties
Crystal structure
Crystals grow in the available open spaces in the rocks, so they take up various shapes
Hardness: most gems are hard
Specific gravity
Color (can be modified or changed)
Refractive index & double refraction
Inclusions (old “flaws”)- may boost price
Mining still primitive (except for diamonds)
Gem deposits
Rare, because the conditions that promote their formations are unusual and thus worthy of scientific study
GEM deposits
Can be classified according to environment of formation or present location
1. Magmatic
2. Hydrothermal
3. Metamorphic
4. Sedimentary
5. Placer
Some can be found in more than one class
1. Magmatic
2. Hydrothermal
3. Metamorphic
4. Sedimentary
5. Placer
Some can be found in more than one class
1. Magmatic
Diamonds found within volcanic kimberlite – names from Kimberley, S. Africa- and lamproite – Argyle mine in W. Australia
Vertical pipe-like bodies called diatremes
Kimberlite forms from a very explosive volatile-rich (high pressure) magma that forms ~ 150 km below the surface. As it travels upwards it fractures surrounding rocks, so kimberlite has many xenoliths (foreign rocks)
Canada’s 1st mine at Ekati, NWT opened 1998
Currently, world’s 3rd biggest producer: Canada
Arkansas has a “diamond park” open to the public (finders-keepers). The eroded surface of an ancient volcanic pipe, 95 m.y. old
Biggest ever found: Cullinan at 3106 carats, the “Star of Africa” – polished 530 carats
2nd biggest from same mine, Cullinan II, at 545 carats- polished 317 carats
Largest diamond in Canada came from the Attawapiskat mine at 35 carats
Canadian diamonds are also called “conflict-free”, but don’t tell that to the Attawapiskatees
Attawapiskat
The rough Cullinan
Sapphires (name means “blue stone” originally used for lapis)
Yellow/green/pink/blue varieties of corundum
Formed deep inside the crust & were brought in basaltic magma. However, they are rare
Economic deposits only found when basalt is weathered & eroded away, leaving behind the heavier minerals such as sapphires & zircons which become concentrated in placer deposits
Corundum Al2O3
Sapphire and Ruby
Second hardest mineral / substance
Synthetic corundum used in optical scanning devises like grocery store checkout counters
Originate in marble / gem gravel deposits
Source thought to be basalt
Ruby can have unique asterism aspect
Madagascar
One of the poorest countries in the world
> 50 % of population below poverty line of $1/day (World Bank)
Has one of the largest gem deposits on the planet
The sapphire trade links some of the poorest people to some of the world’s richest people
Temporary communities hunt along rivers & keep moving
Canada’s 1st sapphire
On Baffin Island, Nunavut
Sampled in 2004 yielded 142 grams
One stone (picture) produced a 1.17 carat sapphire gem – the first in Canada
Ruby
Can also be classified under metamorphic or placer
Other magmatic
Peridot: olivine found in mantle xenoliths
Labradorite: in basalt
Zircon: in granite/basalt/carbonatite
Apatite: in carbonatites
Garnets: in basalt /granite/gneiss
Peridot (olivine)
Found in lavas and rocks from the mantle
Can be mistaken for an emerald
Can also be found in meteorites (pallasites)
Largest gem is 310 carats
A 3 to 4 carat stone sells for $ 40 – 80
Labradorite
From Madagascar
Type location is in Paul’s island, Labrador, but also found in other places
Found in basalt and gabbro
Iridescence produced within crystals of feldspar by light diffraction between “layers”
A pendant, 26 X 40 mm sells for $35
Zircon
Apatite
2. Hydrothermal deposits
Most gemstones formed from volatile-rich fluids in pegmatites
Opal, turquoise
Li & B –rich form tourmaline
F-rich form topaz
Be-rich form beryl or aquamarine
Emerald, also from Be-rich fluids
Volcanic opal also from fluids. It contains many inclusions of water & cracks easily
Ancient mines in Slovakia worked for 2,500 years. Found in Nevada, Mexico & Australia
Amethyst, agates, petrified wood & chalcedony are all varieties of quartz or silica & form from hydrothermal fluids in volcanic environments
Turquoise (means “brought through Turkey”)
Derived from low temp. fluids by the weathering of pre-existing sedimentary phosphate deposits
Mined for 4,000 years
Found in Persia (Iran, country of the “pure”race), Arizona, Mexico
Beware of imitations!
$ 2 to $40 per carat
Aztec God of Fire
Dome of the Rock, Jerusalem
PEGMATITES
The source of the world’s finest tourmaline, beryl & topaz and the main source of more than 70 gemstones
Host to an extreme diverse mixture of exotic minerals & the sole source of very rare minerals
Combination of gigantic crystals & extreme enrichment of rare elements
Baffin Island, Nunavut: white lines are pegmatites
Aquamarine
Important source of Be, Nb, Ta, Sn, Li, Rb, Cs & Ga
Most of the world’s renowned pegmatites are now mined mainly for gems
Pegmatites come in many sizes & shapes
Their internal structure can be simple (all crystals same size), zoned (layers of many sizes of crystals), while the complex have superimposed areas of later alteration with other minerals
Complex pegmatites have pockets or vugs lined with beautiful gem crystals
The main ingredients of most pegmatites are quartz, feldspar and mica
Gems may form layers in between the above or as pockets
Fluids rich in
H2O, B, Li, F, P, CO2
Rare elements such as Cs, Ta, Nb, REE, Zr, U, Sn
“Gem pockets”
Colorado
Tourmaline
Great variety of colors and compositions
A boron silicate with many other metals
Found worldwide
A large cut gem of 191 carats, flawless oval from Brazil was presented in Montreal in 2009 for selling purposes
Another from Mozambique sells for $ 5,000 per carat
Topaz
A silicate with aluminum and fluorine
Name from name of a small island in the Red Sea (Topazos) where a yellow stone was mined
It may not be the mineral we call topaz today
Price per carat: from $10 to $700
Colorless variety
Yellow variety
Beryl
Price per carat: $30 to $200
A beryllium silicate
Name means “precious blue –green color –of-sea-water stone”
Aquamarine: blue variety of beryl
Means “water of the sea”
Color can change or be improved by irradiation
Emerald: green variety of beryl
Symbol of immortality for 4000 years
Cleopatra’s mine was thought to be the only source
Now, it is possible to track gem to it source, country and individual mine!
They have very specific oxygen isotope levels, reflecting composition & temp. of the fluids that deposited them as well as the rocks that its elements flowed through
“The Secret Life of Emeralds”
To measure the isotopes, bombard gem with a beam of charged caesium atoms
Those from the Holy Crown in France came from the Swat-Mingora distruct in Pakistan, a big surprise to the investigators
Another surprise was emeralds in India came from Columbia!
Columbia emeralds are unique, rich in color, clarity and bigger crystals
Green color due to trace amounts of chromium and some vanadium
Relatively rare stone, hence it is very pricy
Price per carat: from $20 to $500 or much higher
Hardness 7.5 to 8 (one of the hardest substances)
Canada’s emeralds
Yukon: found in pegmatites, are Vanadium-rich, discovered in 1998
Dryden, Ont. emeralds
3. Metamorphic deposits
Garnet, lapis, zoisite, ruby & emerald
Most rubies in high-grade meta. rocks like gneiss & marble –Burma the largest producer
Most of world’s emeralds mined in carbonaceous schists in Colombia
Lilac/purple variety of cordierite (iolite) in gneiss (in Manitoba)
Jade (green due to Fe)
World’s toughest stone
Mixture of two minerals: jadeite & nephrite
Lillooet area has the world’s biggest reserves
Prized for its toughness & its almost mirror finish when polished
When hit with a hammer, it produces tiny, feathery cracks, unique for jade
Jade is an aggregate of two minerals, jadeite (pyroxene) & nephrite (amphibole)
Very tough, the two minerals are strongly interlocking
Jadeite is glassy, bright & crystalline. Found mostly in Burma
Nephrite is what the Chinese have venerated for millenia. BC has reserves to meet world demand for several hundred years
Unworked
Display at Jade City, BC
Bringing more pieces
China jade worth more than gold
Prospecting for jade in Jade River, China
Garnet
Six varieties with different names
Differences in chemical composition and color
Used as gemstones and abrasives (sandpaper) since the Bronze Age
Also, sand blasting and wood finishing
Abundant supply in mineral sands in India & Australia
Deep red colour
Lapis Lazuli “heaven stone”
Means “stone of the blue”
In ancient times known as “sapphirus”, which today we use for the blue corundum (sapphire)
One mine in Afghanistan, 7,000 years old (Sar-e-Sang) in the region called Badhakshan (name from ancient Greek Balaskia, which means the Vault). Treacherous terrain of precipitous mountains
Flourishing trade due to its unusual color
Color due to sulfur-rich mineral, also contains grains of pyrite & white marble
4. Sedimentary deposits
The most valuable is precious opal
Some deposits are complete replacement of fossil shells, dinosaurs, belemnites, etc
Others are as replacement layers within sedimentary rocks, but discontinuous & as small pods a few cm thick
Opal, Australia
Coober Pedy, Australia
Opalized bivalve (seashell)
250,000 mine shafts!
“Opal capital of the world”
“dugout”
Coober Pedy
In the middle of the desert
To avoid extreme heat of the summer people dug underground houses. They remain at constant temperature. Cost as much to build as house on surface. You can do mining at the same time
Prospectors given 15.3 m2 parcels of land to explore. No large-scale mining allowed
5. Placer deposits
Because of their toughness and resistance to erosion, gemstones are relatively abundant as placer deposits along rivers
Diamonds, sapphires, zircons, topaz, rubies, garnets, agates & petrified wood
Mineral sands: everyone, every day are using them
Paint on the wall, color in clothing, printing inks, ceramics on the wall, TVs, computers, make-up, medicines, etc
Ilmenite
Zircon
Rutile
monazite
Where?
India, Australia, Brazil
All these minerals are heavier than normal rocks, so they tend to separate
Important source of REEs, Ti, Th, Zr and gems like diamond, sapphire & garnet
Low-grade operations. Only in some countries, there is rehabilitation after mining (Australia, Namibia, Chile)
Ilmenite (TiO2)
Weakly magnetic (contains some Fe)
Difficult to distinguish from magnetite, but it has a white rim of leucoxene
Main source of Ti metal
Main Ti mineral in the Cross Lake deposit
The Vanadium content of the Cross Lake is not good for processing
Its powder is white
Black ilmenite with leucoxene rim
Ilmenite (titanium)
Refined as TiO2 pigment, one of the whitest substances on Earth. The unique reflective and opaque characteristics of Ti dioxide form the basis for most high quality coloring agents, giving paints and dyes a brilliance rarely seen before the 20th century
Titanium is highly resistant to corrosion in sea water and has the highest strength-to-density ratio of all metals
Zircon
Used in ceramics, refractories, chemical processing and insulation, zircon is one of the toughest materials in existence. Improved technology is creating a demand for zircon as a valuable component of futuristic engines, bearings, computer disc drives and cutting equipment
Zircon silicate in composition, but it may contain REEs, U, Th
To produce zirconium dioxide, one of the most refractory materials known
Zircon’s main use as a opacifier, in ceramics
Due to inertness, durability & hardness, it persists weathering and remains in sands
Valuable mineral for radiometric dating due to small amount of U & Th that it contains
Rutile
Rich in titanium dioxide, rutile is the feedstock for the new generation of pollution-free pigment plants. Raw material for light durable titanium metal, rutile is essential to the aerospace industries. Non-reactive Ti is the most successful “human space parts” material for modern surgery
Has special optical properties (very high refractive index), so used in optics
Used as sunscreens to protect against UV
Composed of TiO2
Most common natural form of TiO2
May also contain iron, niobium & tantalum
Monazite (= to be solitary)
Separated into rare earths, monazite provides elements vital to some of the most exciting developments in modern technology. Computers, medical technology and electronic industries are all dependent on rare earths
A source of Thorium
May also contain He- extracted by heating it
Can be radioactive – used for dating rocks
Ce, La, Th, Nd, Y phosphate
Old monazite mine in North Carolina
Videos on gems
. 1.“Stones of Seduction”: rubies & sapphires
Color of rubies due to chromium
Color of sapphires due to iron & titanium
“Crown Jewels” in the Tower of London, over 350 years old preserved in very clean air
Found in Sri Lanka in alluvial deposits (rivers)
2. (video) Topaz
Place for irradiation in Vancouver
turns them into blue color
yellow “Imperial Topaz” from Brazil is very rare
A Gemologist needs to do tests to prove it is: take a picture, weigh & measure it, look under the microscope, use a refractimeter to test its refractive index & its specific gravity
Value at $ 7,700
3. (video)Colombian Emeralds: “value is in the colour”
Formed with pyrite, so they contain no iron. That makes them glow more & fluoresce in the sun
1,000 year old Muzo mine still using old mining methods with many poor sifting mud in the river hoping to get rich
Emerald Trading Centre in Bogota
People buy there & bring to sell in the USA/Canada Up to $ 9,000 per carat
4.(video) Amber
Poland & Kaliningrad, Russia
Floats because it is lighter than a rock
For jewelry & fossil inclusions
Russians also make “pressed amber” by melting small pieces
Many imitations
EXPERIMENT
Small collection of “sands”: 7 samples
2 from shores of lakes
1 from wind-blown shore of lake
1 from an esker
1 from Michelle’s sand deposit – river/esker?
1 from volcanic island with black sand
1 unknown purple sand (Manitoba)
All tested with a magnet
Magnet will pick magnetite/pyrrhotite, but may also pick ilmenite
The amount of magnetic material will be an indication of how much “mineral sands” we may have in the samples
Results
2 shores of lake: NONE
1 wind-blown from shore: NONE
1 esker : some
1 Michelle’s : some
1 volcanic island: a great deal
1 unknown: lots
Conclusion
Lake shore sand may have been separated, with “heavies” underneath the “lights”
Esker and river sand may be sources of “mineral sands”
Anyone dredging a river bed – to avoid/reduce risk from flooding – can pick up some credits
Other gems in Canada
Sapphire
Ruby
Beryl: emerald & aquamarine
Topaz
Tourmaline
Spinel
Cordierite
Zircon
Peridot
Garnet – almandine
Garnet – pyrope
Garnet – spessartine
Quartz – amethyst
Quartz - citrine
Corundum
Nunavut
Ontario
BC
Newfoundland
Beryl (emerald)
Ontario: Dryden area
NWT
Yukon
Nunavut
Beryl (Aquamarine)
BC
Yukon
Ontario
Quebec
Nova Scotia
Topaz
C
Yukon
Tourmaline
NWT
Quebec
Nunavut
Ontario
Spinel
Ontario
Nunavut
Cordierite (Iolite)
BC
Ontario
Manitoba
NWT
Nunavut
Many applications as insulator, resistor, etc
Manitoba minerals (some are gems)
Staurolite (cross-shaped)
Cordierite
Gypsum rosettes in the soil, esp. in the Floodway
Lepidolite (Li)
Pollucite (Cs)
ALLOYS
Definition
Composed of 2 or more metals or a metal and a nonmetal
Can be a solid solution with a single solid structure
Or it can be other combinations of metal phases
They are created because their properties are superior to those of single metals
Examples
Steel
Solder
Brass
Pewter
Phosphor bronze
Amalgam
Electrum
an alloy NATIVE to Earth
Contains silver and gold
Used for coinage in Ancient Greece
Meteorites may contain alloys of iron and nickel – NOT NATIVE to Earth (only in the core)
First alloy made by humans was bronze – add tin to copper
Meteoritic iron
Was forged to red heat by ancient humans and produced tools, weapons and nails
Quite rare in nature
Pure iron is also very rare – only one place in Greenland
Usually iron is found as oxide – hematite/magnetite
Native copper is more common and stronger than native gold, silver & platinum
Bronze
Stronger than both copper and tin
However, tin is rare, only could be found in Cornwall, UK among ancient peoples
In the Middle East brass was formed by combining copper and zinc – both more common than tin
Amalgams
Mercury smelted from cinnabar for a long time
Mercury dissolves many metals such as gold, silver and tin to form amalgams – alloys in a soft paste that hardens
Mercury can be used to extract gold from the rock
Precious metal alloys
In ancient Egypt & Mycenae (Greece) gold alloyed with copper to make “red gold” or more brilliant gold
Sterling silver has added copper to make it stronger
Pewter
Alloys with tin
Add copper, lead, antimony or bismuth
Steel
Carbon added to iron
Variety of metals mostly nickel, molybdenum and vanadium
Need a blast furnace
Sault St. Marie, Ont., Hamilton, Ont. and Montreal
A trip to the Lapis mines
Badhakshan (Balaskia), Afghanistan
follow the Korcha river
Man wearing “kausia”, ancient Greek hat
Florida restaurant
At the end of the Korcha river
Remains of ancient Greek city, Afghanistan/Tajikistan border, Korcha/ Amur rivers
with a theatre carved out of rock, temples, palaces, sculptures, etc
Remains destroyed & looted by the Taliban in recent years after surviving for 2,300 years!
This advice is carved on a rock:
"As a child learn good manners
as a young man, learn to control thy passions
in middle age, be just
in old age, give good advice
then die, without regret"
as a young man, learn to control thy passions
in middle age, be just
in old age, give good advice
then die, without regret"
PROJECTS
Limestone Plant (grade 100%)
product is quicklime that has many uses: agriculture, paper mills, mines & making cement
Cesium and Tantalum (grade 100%)
Both are mined in Manitoba
Cesium burns with blue colour, ignites in water, used in drilling muds, etc
Tantalum has high-temperature applications, in electrical devices & surgical implants
Amethyst Mining (grade 100%)
the darker the colour the higher the price
the colour is due to iron and fades in the sun
Thunder Bay: largest mining area in N. America
The Alkali metals (Lithium, Potassium and Sodium) (grade 100 %)
All are used in fireworks and explode in contact with water
Lithium used in batteries, ceramics, etc
Potassium used in fertilizers, the Salt Lamp, etc
Sodium used in street lights, winter roads, etc
Manitoba Nickel (grade 95%)
The "Thompson Nickel Belt" contains most of Manitoba's Nickel deposits
The host rock is serpentinite and the deposits are found by geophysics (gravity & magnetic surveys)
Nickel has many uses, such as in alloys, rechargeable batteries & electronics
Nickel products can be recycled
Gypsum (grade 95%)
It is the "wonder mineral" in construction
The "Plaster of Paris", first used in Paris, France
Has many many uses that includes the principal component of toothpaste
product is quicklime that has many uses: agriculture, paper mills, mines & making cement
Cesium and Tantalum (grade 100%)
Both are mined in Manitoba
Cesium burns with blue colour, ignites in water, used in drilling muds, etc
Tantalum has high-temperature applications, in electrical devices & surgical implants
Amethyst Mining (grade 100%)
the darker the colour the higher the price
the colour is due to iron and fades in the sun
Thunder Bay: largest mining area in N. America
The Alkali metals (Lithium, Potassium and Sodium) (grade 100 %)
All are used in fireworks and explode in contact with water
Lithium used in batteries, ceramics, etc
Potassium used in fertilizers, the Salt Lamp, etc
Sodium used in street lights, winter roads, etc
Manitoba Nickel (grade 95%)
The "Thompson Nickel Belt" contains most of Manitoba's Nickel deposits
The host rock is serpentinite and the deposits are found by geophysics (gravity & magnetic surveys)
Nickel has many uses, such as in alloys, rechargeable batteries & electronics
Nickel products can be recycled
Gypsum (grade 95%)
It is the "wonder mineral" in construction
The "Plaster of Paris", first used in Paris, France
Has many many uses that includes the principal component of toothpaste
