Tuesday, 31 December 2013

Treasures of the British Museum I

Cross pendant. Gold with a closed back and set with a central pearl surmounted by a garnet and an emerald, flanked by hessonite garnets, a sapphire, and a zircon with a ruby, a chrysoberyl cat's eye, an amethyst and a zircon below. Date 1800 (circa)

Gimmel-ring; gold; enamelled; bezel, set with ruby and emerald, in form of quatrefoil flower with pendant leaves decorated with blue, black and white scrolls; inner faces of bezel decorated with scrolls; shoulders moulded in form of scrolls; inscription on inner surfaces revealed when ring opened. Date 16thC, Germany.
Pendant in the form of an animal head. Made of wood and covered with turquoise and malachite mosaic held in place with pine resin adhesive. The eyes are made from pyrite and white and yellow striped conch (Strombus) shell. The open mouth is encrusted with gemstones (garnet, beryl, emerald, spinel, zircon) and lined with sharks teeth. The pearls, gemstones and teeth are all held in place with beeswax. Culture/period Mixtec; Aztec

Two-colour gold comb-mount in the form of a leafy twig surmounted by a bird, with a ruby eye and ring in its beak, on a trembler spring. The branch is set with gemstones whose initials spell 'dearest', ie. diamond, emerald, amethyst, ruby, emerald, sapphire and turquoise. There is a hair compartment in the reverse of the bird. Date 1830 (circa) England.
Intaglio of rock crystal: massive, oval, convex on one side, flat on the other. On the flat surface is engraved the Crucifixion between the Virgin and St John; Christ has the cruciferous nimbus and wears a loin-cloth, his head is inclined; cross is plain, without titulus, serpent coiled round its foot; Virgin and St John stand bending forward, raising their mantles to their faces in attitudes of grief; above cross are two medallions containing busts of the sun and moon holding torches, former radiate and wearing chlamys, latter as female figure in mantle with head surmounted by crescent; in modern metal mount; each side of crystal with cylindrical drill-hole. Culture/period : Carolingian Date 846-869 (?)

Gold memento-mori fede-ring. This large ring, either intended as a thumb-ring or to be worn over a glove on the finger, is made of gold, enamelled and set with gemstones. The bezel is in the form of a book, placed horizontally, the upper cover being set with four table-cut gemstones in plain gold collets: a diamond (lower right), a ruby (upper right), an emerald (lower left) and a sapphire, or blue spinel (upper left); in high relief between the gemstones, in the centre, is a white-enamelled skull with a green-enamelled toad above and another below, and two snakes issuing from the skull to left and right. Date 1526-1575

Saturday, 28 December 2013

Synthetic Diamonds

The closest synthetic approximation to diamond is a man-made diamond. Man-made diamonds can be made of pure carbon.
The Gemological Institute of America (GIA) recognizes these as real diamonds from a compositional perspective. But, the man-made diamonds don't have the rich geological history that natural diamonds do. Laboratories simulate the heat and pressure from the Earth's mantle that create natural diamonds. For some, diamonds come down to a matter of time and money: days versus millions of years, thousands of dollars versus tens of thousands of dollars or more.

If a uniquely coloured, relatively inexpensive diamond is desired, man-made ones in shades of orange, yellow, pink and blue are readily available. Finding a large diamond will prove a greater challenge -- most man-made diamonds weigh less than one carat. To prevent retailers from passing off man-made diamonds as natural ones, the GIA is selling machines that will help jewelers easily distinguish between the two.

It may come as no surprise that the developer behind these machines is none other than the king of the natural diamond industry: De Beers.

Tuesday, 24 December 2013

Star Sapphire

A star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism; red stones are known as "star rubies". Star sapphires contain intersecting needle-like inclusions following the underlying crystal structure that cause the appearance of a six-rayed "star"-shaped pattern when viewed with a single overhead light source. The inclusion is often the mineral rutile, a mineral composed primarily of titanium dioxide.

The value of a star sapphire depends not only on the weight of the stone, but also the body color, visibility, and intensity of the asterism.
Star Sapphire is usually found in blue colors, but there are also various shades of brown and green that are called black star sapphire. Orange and yellow star sapphires are almost unknown, and very rare. Color changing star sapphires are even more of a rarity.

The coloring agents in blue sapphire are iron and titanium and, in violet stones, vanadium. A small iron content only results in yellow and green tones, chromium produces pink, iron and vanadium orange tones.
The most desirable color is a vivid, intense blue.

Less transparent sapphires, translucent or opaque stones, are cut en cabochon to support the star effect with its six rays. The best cabochons are somewhat transparent, with smooth domes of good symmetry.
The Star of India is a 563.35-carat star sapphire, one of the largest such gems in the world. It is almost flawless and is unusual in that it has stars on both sides of the stone. The greyish blue gem was mined in Sri Lanka and is housed in the American Museum of Natural History in New York City.
The Black Star of Queensland is a 733-carat black sapphire, and the world's largest gem quality star sapphire. It was discovered in Australia in the 1930s.

Sunday, 22 December 2013

Cool Gold Coins for Sale

A Medeival Islamic gold dinar coin from the Ilkhanid Period struck circa 1256 - 1335 A.D.

$ 895
Medieval English Hammered Gold Pound Sovereign Coin of Queen Elizabeth I - 1594 ELIZABETH D G ANG FRA ET HIB REGINA

"Elizabeth by the Grace of God Queen of England France and Ireland"

"May the Shield of Faith Protect Her".

Byzantine gold solidus of Emperors Constantine V Copronymus, (dung-named) Leo III and Leo IV struck circa 741 - 775 A.D. at the Syracuse mint. The obverse depicts the facing busts of Constantine V, bearded and Leo IV, beardless, each wearing chlamys, cross on staff of pellets between. $1,950.00
A solid gold ancient Byzantine solidus of Emperor Phocas, struck 603 - 604 A.D. Minted in Carthage. The obverse depicts the bust of Focas, shown with cross-topped crown and holding the globus cruciger in his right hand.

The globus symbolises Christ's authority over the world, and by proxy the authority of the Byzantine ruler. The legend reading: D[ominvs] N[oster] FOCAS PERP[etvvs] ANZ

"Our Lord Focas, Perpetual Emperor"

Friday, 20 December 2013

The Gold of Devils Tower

Near the northeast corner of Wyoming is a striking mountain of igneous rock that looks like a gigantic tree-stump. Columns run vertically up the top part of the rock like giant scratches. The name given to the mountain by the white man was "Devils Tower." The Indians had many names for it. One of them was "Bear Lodge."
According to legend, while exploring the rocks at the base of the mountain, natives discovered a passageway underneath it. They made torches out of pitch pine knots for light and started exploring the tunnel. They found the passage strewn with bones. Perhaps human bones.

At the end, the tunnel opened up into a cave with an underground lake some 25 yards long and more than 15 yards wide. Around the lake were large quantities of gold.
No hidden passages have ever been found. Geologists agree that Devils Tower was formed by the intrusion of igneous material, but they cannot agree on exactly how that process took place.

In 1906, President Theodore Roosevelt established Devils Tower as Americas' first national monument.

Thursday, 19 December 2013

World's most expensive necklaces

Chopard Magnificent Diamond and Emerald Necklace - This extraordinary necklace features 191 carats of emeralds, set between 16 carats of diamonds. Price: $3 million
Titanic Heart of the Ocean Diamond - The “Heart of the Ocean” diamond necklace that Kate Winslett wears in the movie ‘Titanic’ is not a real diamond. It’s actually a blue cubic zirconium made by London jewelers Asprey & Garrad. The jewelers did later make a reproduction using real gems (including a heart-shaped Ceylon sapphire that weighs in at a whopping 170 carats). Price: $3.5 million
De Beers’ Marie Antoinette Necklace features more than 181 carats of diamonds, including a monster 8 carat, pear-shaped white diamond as a centerpiece. All of the jewels are set in platinum. $ 3.7m.
Neil Lane’s Diamond Necklace features 140 carats of pear-shaped, cushion-shaped and teardrop-shaped diamonds, all set in platinum on multiple strands. $4m.
Garrard’s Heart of the Kingdom Ruby necklace features as its centerpiece a nearly 41-carat, super rare, heart-shaped Burma ruby. The brilliant stone is surrounded by more than 150 diamonds. Price: $14 million
The most expensive necklace ever made will be on sale at Singapore's JewelFest show. It is estimated to bring $55 million.

The jewelry, known as L'Incomparable, features a large yellow stone suspended from a rose gold setting with 90 white diamonds and weighs 637 carats in total.

The necklace was made by luxury jeweler Mouawad and features a yellow, internally flawless diamond weighing 407 carats with 90 white diamonds weighing nearly 230 carats. The rough stone was found in a pile of mining tailings by a young girl in the Democratic Republic of Congo.