Sunday, 28 February 2021

King Tut's jewels made of desert glass

In 1922 Howard Carter was searching the tomb of Tutankhamun and found a large breastplate, decorated with gold, silver, various precious jewels and a strange gemstone. Carter identified it as chalcedony, a common variety of quartz.

Ten years later pieces of glass were found in the Libyan Desert along the border of modern Egypt. The pale yellow and translucent material was identical to that found in Tutankhamun's tomb.
Libyan Desert glass (LDG), is an impactite with fragments found over areas of tens of square kilometers.
Tektites are natural glass formed from terrestrial debris ejected high into Earth's atmosphere during meteorite impacts. LDG is almost pure silicon-dioxide, like quartz, but its crystal structure is different. It also contains in traces an unusual combination of elements, like iron, nickel, chromium, cobalt and iridium.
It's thought LDG formed 28 to 26 million years ago when an impact melted the quartz-rich sands of the desert.

Saturday, 27 February 2021

Royal Spinel - Balas Ruby

Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.

After the 18th century the word ruby was only used for the red gem variety of the mineral corundum and the word spinel became used. "Balas" is derived from Balascia, the ancient name for Badakhshan. For centuries it was the main source for red and pink spinel.

Cartier Royal ring, platinum, 20.02 carat emerald-cut pink spinel, onyx, brilliants.
Spinel is most famous for its deep red variety that closely resembles ruby. The two gemstones can be very difficult to distinguish. Until the late 19th century, there was no distinction made between ruby and red spinel, as they look identical and are found in the same localities. Many famous old "rubies" were discovered to be spinel.

Mining in Afghanistan has a history over 2,000 years. Afghanistan's ruby/spinel mines were mentioned in the writings of many early travelers. The Badakhshan mines were of great importance during the period from 1000–1900 AD. They were the source of many of the finest early red spinels in gem collections around the world.
The crown jewels of Iran, the collection in Istanbul's Topkapi, Russia's Diamond Fund, and England's Tower of London all contain fine spinel.
Black Prince Ruby

The Hope spinel sold for a record £962,500 in late 2015

Imperial Mughal necklace sold in 2011 for $5,214,348
Samarian Spinel - 500 carats, largest known
Pink and Purple Spinel Ring

Friday, 26 February 2021

Spinel on the rise

Termed “the great impostor,” for hundreds of years it was believed that spinels and rubies were the same stone. With a rich color that is described as “stoplight red” even experts couldn't tell the difference. In 1812 Friedrich Mohs published the scale which is used today to define the relative hardness of gemstones. Ruby (corundum) was identified as a 9, while spinel was 7.5 to 8.

Spinels were used in jewelry throughout the 1800s and early 1900s, but it was now perceived as a Class B gem.
One of the rarest hues found in spinel is a cobalt blue Vietnam natural spinel. Spinels were often known as ‘Balas ruby,’ a name probably derived from the North Indian region of Balascia (or Badakshan.)” The finest spinels display a bright, vitreous luster. Those that exhibit a strong, even, perfectly saturated hue are most prized. When expertly cut, they exhibit brilliance and exceptional clarity. While a ruby might go for $40k a carat, a spinel of the same size and quality would garner $1k to $7k a carat.
The spinel is now called “the collector’s gemstone”or “a connoisseur’s stone.”

See ----->Royal Spinel - Balas Ruby

Wednesday, 24 February 2021

Gemstones of Pailin, Cambodia

The southeastern corner of central Thailand along the Cambodian border has been an important source of fine ruby and sapphire for centuries. Pailin is at the edge of the Cardamom Mountains in the west of Cambodia, 25km from the border of Thailand. Pailin was a prosperous town due to its gem deposits. Those resources attracted the attention of the Khmer Rouge.
Sapphire mining near Pailin using high-pressure water to turn the gem rich gravels into mud. The mud is then processed.
The Khmer Rouge were Cambodian Communists who mounted an insurgency against the national government in 1967 and succeeded in taking power in 1975 under leader Pol Pot. They ruled for 4 years until they were ousted by the Vietnamese army in 1979.
The Khmer Rouge regime was distinguished by the genocide of an estimated 1.5m people.
The blue sapphire from Pailin are highly regarded. They range in colour from light to deep blue, but with a distinctive purity and intensity of color. The Khmer Rouge used proceeds from mining Pailin sapphire to fund their offensive and later their government once they gained national power.

Pailin sapphire was one of the first "blood gemstones."
The first stones to be treated with heat to improve their colours originated from Pailin mines. Cambodia is famous for gem treatment.
The precious stone industry in Pailin is dwindling with deposits largely depleted. Cambodia's gems are declining sharply.

Sapphire mining was not the only digging in Pailin. It is one of the most heavily landmined areas in the world.

Tuesday, 23 February 2021

Green Diamonds

The 5.03 carat Fancy Vivid Green 'Aurora Green' made $16.8m or $3.3m per carat in 2016.
Green diamonds are among the rarest of all fancy colors. The green color is caused by exposure to radiation and is extremely unique. Natural radiation creates an external skin or surface of green color. It is uncommon for the green color to reach deep within a diamond.

Labs may be unable to conclusively determine the natural origin of green diamonds because the cause is radiation.
Lab graders assess the natural color of green diamonds by this skin. Irradiated green diamonds are found in the marketplace, so determining natural color for value is key.
Green is the color between blue and yellow, so common secondary colors in green diamonds include bluish green and yellowish green, and if the color is desaturated, grayish green or brownish green.

1.56 carat, Fancy Vivid Green Diamond
Natural green diamonds are second to red diamonds as the world's rarest fancy color. True greens devoid of secondary hue are the most valuable. The green diamond has a very strong emotional correspondence with safety as it is the most restful color for the human eye. Green suggests both stability and endurance. Aqua green is associated with emotional healing and protection while Olive green is the traditional color of peace.
The Dresden Green is a 40.7 carat, pear shaped stone with a VS1 clarity grade. It is one of the largest and finest natural green diamonds ever discovered.
The Ocean Dream The diamond is a 5.51-carat, fancy deep blue-green, shield-shaped diamond.

It is the only natural diamond known with this color combination.
The Chopard Chameleon, is a 31.31ct Oval-cut diamond which appears green in bright light but looks yellow in darkness. This stone was one of the first reported by the GIA as a chameleon in the late 1950s.

Cushion-shaped fancy intense green diamond weighing 6.13 carats, within a brilliant-cut pink diamond surround, extending to the half-hoop, mounted in 18k rose gold.

A square-shaped fancy green diamond weighing 10.36 carats, set in a ring within a pear-shaped and round cut pink diamond surround.

3.15 carat, Fancy Intense Yellowish Green diamond. VS1.
Fancy vivid green diamond weighing 2.52 carats. It made $ 3,106,500 CHF at Sotheby's in 2009.