Emerald (Be₃Al₂(SiO₃)₆) is a variety of the mineral beryl, colored green by trace amounts of chromium and sometimes iron. It is highly prized as a gemstone and by weight is the most valuable gemstone in the world, although it is often made less so by inclusions, which all emeralds have to some degree. Beryl has a hardness of 7.5 on the 10 point Mohs scale of hardness. However, this Mohs rating can decrease, depending on the number and severity of inclusions in a particular stone.

Most emeralds are oiled as part of the post lapidary process. The amount of oil entering an emerald microfissure is roughly equivalent to the size of a period in print.

Emeralds come in many shades of green and bluish green. There is a wide spectrum of clarity, along with various numbers of inclusions. Most emeralds are highly included, so it is quite rare to find an emerald with only minor inclusions. Because of the usual inclusions, the toughness (resistance to breakage) is classified as generally poor.

Emeralds in antiquity were mined by the Egyptians and in Austria, as well as Swat in northern Pakistan.

A rare type of emerald known as a trapiche emerald

is occasionally found in the mines of Colombia. A trapiche emerald exhibits a “star” pattern; it has raylike spokes of dark carbon impurities that give the emerald a six-pointed radial pattern. It is named for the trapiche, a grinding wheel used to process sugarcane in the region. Colombian emeralds are generally the most prized due to their transparency and fire. Some of the most rare emeralds come from three main emerald mining areas in Colombia: Muzo, Coscuez, and Chivor. Fine emeralds are also found in other countries, such as Zambia, Brazil, Zimbabwe, Madagascar, Pakistan, India, Afghanistan and Russia.

The value of an emerald depends on cut, color, clarity, and carat. The characteristics of Colombian emeralds set the highest standards of quality.

Synthetic emerald Emerald is a rare and valuable gemstone and, as such, it has provided the incentive for developing synthetic emeralds. Both hydrothermal and flux-growth synthetics have been produced, and a method has been developed for producing an emerald overgrowth on colorless beryl. The first commercially successful emerald synthesis process was that of Carroll C. Chatham. Because Chatham’s emeralds do not have any water and contain traces of vanadate, molybdenum and vanadium, a lithium vanadate flux process is probably involved. The other large producer of flux emeralds is Pierre Gilson Sr., which has been on the market since 1964. Gilson’s emeralds are usually grown on natural colorless beryl seeds which become coated on both sides. Growth occurs at the rate of 1 mm per month and a typical seven-month growth run produces emerald crystals of 7 mm of thickness (Nassau, K. Gems Made By Man, 1980).

Hydrothermal synthetic emeralds have been attributed to IG-Farben, Nacken, Chatham and others, but the first satisfactory commercial product was that of Johann Lechleitner of Inbruck, Austria, which appeared on the market in the 1960s. These stones were initially sold under the names “Emerita” and “Symeralds”, and they were grown as a thin layer of emerald on top of natural colorless beryl stones. Although not much is known about the original process, it is assumed that Leichleitner emeralds were grown on acid conditions. Later, from 1965 to 1970, the Linde Division of Union Carbide produced completely synthetic emeralds by hydrothermal synthesis. According to their patents (US3,567,642 and US3,567,643), acidic conditions are essential to prevent the chromium (which is used as the colorant) from precipitating. Also, it is important that the silicon containing nutrient be kept away from the other ingredients in order to prevent nucleation and confine growth to the seed crystals. Growth occurs by a diffusion-reaction process, assisted by convection. Typical growth conditions include pressures of 700-1400 bars at temperatures of 500 to 600°C with a temperature gradient of 10 to 25°C. Growth rates as fast as 1/3 mm per day can be attained.

Flux-grown synthetic emeralds fluoresce a dull red with long wave ultraviolet light, due to an indicator added during the process of synthesizing the emerald, whereas natural specimens do not.

Synthetic emeralds are often referred to as “created”, as their chemical and gemological composition is exactly the same as its natural counterparts. The Federal Trade Commission (FTC) has very strict regulations as to what can and what cannot be called “synthetic” stone. The FTC says: “…[created stone must have] essentially the same optical, physical, and chemical properties as the stone named.” Furthermore, all natural emeralds, with the exception of the red Bixbite beryls from Utah which are anhydrous, have water inclusions, as emerald is of hydrothermal origin. Flux synthetic emeralds have no water, an integral part of any natural beryl (this also accounts for flux-grown emeralds being more stable when subjected to high temperatures). Hydrothermally-grown emeralds, however, contain water molecules.

Cultural and historical/mythical usage

Emerald is regarded as the traditional birthstone for May , as well as the traditional gemstone for the astrological signs of Taurus and Cancer.

According to Rebbenu Bachya, the Hebrew word “Nofech” in Exodus 28:18 means “Emerald”, and was the stone on the Ephod representing the tribe of Judah. According to other commentaries, “Nofech” means “garnet”, and another stone, the “Bareqet”, representing the tribe of Levi, is thought to be emerald.

In some cultures, the emerald is the traditional gift for the 55th wedding anniversary. It is also used as a 20th and 35th wedding anniversary stone.

Grawin, Glengarry, and Sheepyard Opal Fields.

I bumped into Steven and asked him if he would like to talk about the opal fields near his home. He submitted this article and pictures.

Hi Gary,
Here is the brief history and present day story about Grawin, Glengarry, and Sheepyard Opal Fields.
Cheers
Steven

The Sheepyard opal field is located approximately 75km west of Lightning Ridge, NSW and forms part of a triangle of opal fields consisting of Grawin, Glengarry and Sheepyard
Opal was first discovered at Glengarry in 1905 by Mr Charles Phipp who was working on Morendah Station at the time, but little mining was done there. The Grawin was established in 1908 with the discovery of the opal at “Hammond Hill”. Further discoveries in 1920 at “Richards Hill” put the unofficial village on the map. Since the first discovery of opal in the region, people have come and gone in tides with each new strike, seeking their fortune in search of the rainbow in the rock. At the time mining was done by candle light with a hand pick and the waste was removed by shovel and bucket and wound up by hand with a wooden windlass. In 1928 an opal weighing almost 450g, and the size of a man’s fist was found at Richards Hill and caused a rush of men to this field. The opal was named “The Light of the Worlds” and is still the best known opal from this area. After the Second World War things began to get more mechanical with the electric generator for light and motorised hoisting gear to make the removal of waste quicker and a bit less like slave labour. Then came the electric jackhammer and the amount of dirt that could be removed increased and the bucket was replaced by wheelbarrows and all sort of inventions to make the job better for the miner and in turn caused an increase in the number of people who came to have a go. The next major rush was started on Melbourne Cup Day in 1985 when the Sheepyard Rush was found. The Sheepyard area was named after a stumble on of opal near the fence of the old Sheepyard. By now the piles of dirt were starting to fill the landscape and this lead to the Short Throw self tipping hoist and tip trucks to remove waste. This led to the invention of the rickshaw to wheel waste to the hoist bucket. By the time the 90′s came along a new rush called Carters Rush had started and Blowers (Giant Vacuum Cleaners) were in use as well as underground hydraulic diggers and mini loaders and as many different inventions as there are miners are now being used in search of the thing that all miners, young and old lust after, “The Rainbow in a Rock”

https://teirockdrills.com/wp-content/uploads/2018/01/TEI_MME250R_mini_drill-800-1.jpg

Prospecting_with_drill

http://www.minerals.net/glossarymain.aspx GET HARD DATA HERE! http://www.minerals.net/

Opal

Although mining at Glengarry was also going on for some time it was not until about 1970 when a find of some very good opal was made that Glengarry became the new “Hot Spot.” The Mulga Rush, which began in 2000, is the biggest opal rush since the Coocoran was discovered in the early 1900′s.

https://youtu.be/lE2j10xyOgI -click- 1964 Quake: The Great Alaska Earthquake

Free Geology Books!

Filed under: Free Books — Gary September 9, 2011 @ 1:33 pm

I found this site offering free geology books. 51 books on this page alone:

http://worldofgeology.weebly.com/free-geologic-books-1.html

And 18 books on this page:

http://worldofgeology.weebly.com/free-geologic-books-2.html

Samples of the books below:

Free_fossil_books

Free_gemmology_books

Free_gems_book

Free_Mineralogy_books

Free_palaeontology_books

Free_quartz_books

Free_Rock_books

ENJOY! http://rockhoundblog.com/category/free-books/

RELATED
Diamond Macle PUBLICATIONS

Canadian Consulting Engineer Magazine
www.canadianconsultingengineer.com

Eco Log ERIS
www.ecologeris.com

Eco Log Week
www.ecolog.com

Hazardous Materials Management Magazine
www.hazmatmag.com

Machinery and Equipment MRO Magazine
www.mromagazine.com

The Northern Miner Newspaper
www.northernminer.com

OHS Canada Magazine
www.ohscanada.com

Scott's Directories
www.scottsdirectories.com

Solid Waste & Recycling Magazine
www.solidwastemag.com

Polymer Search on the Internet
www.polymer-search.com

___________________________________________________________________________________________________________________________________

Module B. Colour from the Cosmos Lesson 17: Corundum Mineralogy and Gemology

What is Corundum and What are its Basic Qualities?

Corundum is an aluminum oxide that commonly forms hexagonal barrel-shaped prisms that taper at both ends or as thin tabular hexagonal plates. It has a hardness of 9 on the Mohs scale, making it one of the most durable commercial gemstones. It has no dominant cleavage and fractures in a conchoidal manner. A high density of ~4.0 g/cm³ (most silicate minerals are ~2.6 g/cm³) results in corundum occurring in secondary placer deposits and recoverable by panning methods, similar to how you would recover placer gold.

Corundum comes in all colours of the rainbow but is most commonly found as opaque crystals with dull colours. Red corundum is called ruby, blue corundum is called sapphire, and all other colours are called fancy sapphires. Some varieties of corundum will fluoresce under short wave and long wave UV light if there is enough chromium in the crystal structure but little iron, which tends to quench any emitted energy.

http://www.eos.ubc.ca/courses/Dist-Ed/eosc118-webpromo/01-modB-les17-webpromo.htmlWhat Colours can Corundum Have, How are These Colours Generated, and What Gem Varieties Result? (more photos)

Pure corundum is colourless and clear if transparent or pale white if opaque. This mineral also has low dispersion so the value of the stones comes not from fire generated (as in diamond), but rather from the intensity of colours seen. The vivid colours of corundum gem varieties, such as ruby and sapphire, arise primarily from elemental substitution in the Al site by transition metal elements. The most common cations to substitute are Fe⁺², Fe⁺³, Ti⁺⁴, Cr⁺³, and V⁺³.

A continuum of colour saturation exists between pink sapphire and ruby that is correlated with trace amounts of Cr. There is no official cutoff for the amount of Cr needed for ruby, but usually rubies will have up to ~1 wt% of Cr₂O₃. When Cr substitutes for Al, wide absorption bands are generated in the violet (~450 nm) and green-yellow (~500 nm) ranges, as well as overlap a bit into the blue region. The red region of the electromagnetic spectrum (~650 nm) does not have very much absorption at all and results in all colours but red being blocked by ruby.

But there is another trick up ruby's sleeve that makes its red almost jump out at the observer. When Cr is introduced into corundum it makes the mineral fluorescent under UV light. This means that UV energy from normal light is accepted into the crystal and then re-emitted at a lower energy level - conveniently in the red region, thus amplifying the intensity of red in ruby under daylight conditions. However, if any iron is present it will usually absorb the red fluorescence from UV light. Thus, the finest rubies are those that have little to no iron in their crystal structure.

Blue sapphires are generated primarily from pairs of Fe⁺² and Ti⁺⁴ substituting into the crystal structure for Al⁺³. The process of intervalence charge transfer (essentially continual swapping of electrons, bouncing back and forth) occurs between the Fe and Ti and all colours except blue are absorbed. So like ruby, it is the absorption of all other colours from full spectrum light (aka white light) that generates the beautiful blues in sapphires, rather than the "generation" of the blue colour. Very small amounts of these elements (only ~0.01 wt% Fe and Ti) are needed to produce the vivid blues.

Other colours are generated from a combination of these elements, as well as other minor cations and defects in the crystals. Also, a single corundum gemstone can be multi-coloured from different concentrations of metals in different parts of the crystal - this is called zoning.

Some sapphires also show an optical characteristic called asterism, which is most commonly seen as a six or twelve pointed star. These "arms" of the star are generated from oriented inclusions of long and skinny minerals (almost always the mineral rutile, a titanium oxide, TiO₂). Specimens found with these inclusions are often cut and polished in a rounded and polished cabochon style to emphasize the nature of this optical effect. Rutile inclusions can occur in both sapphires and rubies, although it is more common in sapphires.

Sapphires

Size, carats	Approximate value per carat, USD
Less than 0.5	$175 to $200
0.5 to 1.0	$200 to $350
1.0 to 2.0	$350 to $600
2.0 to 5.0	$600 to $1000
More than 5.0	$1000 to $2500

__________________________________________________________________________________________________________________________________________________

SUPPORT ORGANIZATIONS

British Columbia & Yukon Chamber of Mines
www.bc-mining-house.com/chamber

Canadian Association of Mining Equipment & Services for Export
www.camese.org

Canadian Copper and Brass Development
www.ccbda.org

Canadian Institute of Mining, Metallurgy and Petroleum
www.cim.org

Canadian Mining Industry Research Organization
www.data.ctn.nrc.ca

Canadian Nuclear Associationion of Canada
www.cna.ca

The Coal Associat
www.coal.ca

The Gold Institute
www.goldinstitute.org

International Cadmium Association
www.cadmium.org

International Copper Association, Ltd.
www.copper.org

Mines and Aggregates Safety and Health Association
www.masha.on.ca

The Mining Association of Canada
www.mining.ca

Mining Suppliers, Contractors & Consultants of British Columbia
www.mining.bc.ca

Nickel Institute
www.nidi.org

Northern Centre for Advanced Technology Inc.
www.norcat.org

Northwest Territories Chamber of Mines
www.miningnorth.com

Ontario Mining Association
www.oma.on.ca

Prospectors & Developers Association of Canada
www.pdac.ca

The Silver Institute
www.silverinstitute.org

Yukon Chamber of Mines
www.hypertech.yk.ca/business/whitehorse/ycmines/chambe

FEDERAL & PROVINCIAL GOVERNMENTS

British Columbia Ministry of Energy and Mines
www.em.gov.bc.ca

Indian Affairs and Northern Development
www.inac.gc.ca

Manitoba Department of Energy and Mines
www.gov.mb.ca/em

Natural Resources Canada
www.nrcan.gc.ca

NRCan CANMET
www.nrcan.gc.ca/mms/canmet-mtb/mmslwelcome

NRCan Geological Survey of Canada
www.nrcan.gc.ca/gsc/

New Brunswick Department of Natural Resources and Energy
www.gov.nb.ca/dnrc

Newfoundland and Labrador Department of Mines and Energy
www.gov.nf.ca

Northwest Territories Department of Resources, Wildlife and Economic Development
www.gov.nt.ca/rwed/mog/index.htm

Ontario Ministry of Natural Resources
www.gov.on.ca

Ontario Ministry of Northern Development and Mines
www.gov.on.ca/MNDM

Prince Edward Island Department of Development
www.gov.pe.ca/edt

Quebec Department of Natural Resources
www.mrnfp.gouv.qc.ca/english/mines/index.asp

Saskatchewan Department of Energy and Mine
www.gov.sk.ca/enermine

nepal