Wednesday, 25 December 2013

Ceylon Sapphires

For centuries, the island of Sri Lanka has been a key source for a variety of gemstones, including sapphires. Sri Lankan gems were mined, set into jewelry, and traded abroad since at least 500 B.C. The Etruscans, Greeks, and Romans coveted sapphires, and the Indians called Sri Lanka “Ratna deepa,” which means “Island of Gems.”
Many consider Sri Lankan sapphires to be among the best in the world.

A range of colored sapphires can be found there, including rare padparadschas. Approximately 90 percent of the world’s star sapphires also come from the island. The sapphires from Sri Lanka are known for their high clarity, rutile silk, and fingerprint inclusions. Current sapphire yields are estimated to be 60 percent blue, 25 percent yellow or orange, and 15 percent pink or purple.
Sri Lanka’s sapphires come from extensive gravel deposits located in the southern two-thirds of the island. Although the original source of this gravel remains unknown, scientists speculate that the parent rock is a Precambrian metamorphic rock that makes up about 90 percent of the island.

Experts speculate that the erosion of this parent rock has created the extensive gem deposits along ancient and current riverbeds in the lower valleys.

Mining methods are relatively primitive and when gravel is extracted from current riverbeds, it is done with hand-made scrapers.
On land, miners typically use simple non-mechanized equipment, including picks, shovels, spades, and baskets. When shafts are sunk to reach the gravel, they are reinforced with palm and bamboo scaffolding and pumped to keep the water level down. At some locations, bulldozers scrape the overburden, but the gem gravel is still washed by hand.

Marco Polo wrote that the island had the best sapphires, topazes, amethysts, and other gems in the world.

Ptolemy, the 2nd century astronomer recorded that beryl and sapphire were the mainstay of Sri Lanka’s gem industry.
Geologically speaking Sri Lanka is an extremely old country. Ninety percent of the rocks of the island are of Precambrian age, 560 million to 2,400 million years ago.
The gems form in sedimentary residual gem deposits, eluvial deposits, metamorphic deposits, skarn and calcium-rich rocks. Other gems are of magmatic origin.

Residual deposits are mainly found in the flood plains of rivers and streams. Metamorphic types of gems constitute 90% of the gem deposits in Sri Lanka. Blue sapphires from Sri Lanka are known as Ceylon Sapphire. Ceylon Sapphires are unique in colour, clarity and lustre compared to the blue sapphires from anywhere else.

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"

Saturday, 21 December 2013

Rockwell Diamonds Inc. recovers 287ct Diamond

(IDEX Online News) – Rockwell Diamonds Inc. has recovered a 287-carat diamond from its operations in the Middle Orange River region in South Africa "which is of commercial color (tinted white) and makeable in shape".

The miner said that as the stone is the fifth large diamond to be recovered from the operation in the past three months, it further reinforces management's decision to focus operations in Middle Orange region. The diamond will be sold into the beneficiation joint venture with Steinmetz Diamonds at market value with Rockwell participating equally in the added value of the polished diamond at sale.

"The stone was recovered from the Saxendrift Extension property acquired in March 2012 and follows the recovery of four plus 100-carat diamonds in September 2013. These results show that our plants are correctly geared for the recovery of large diamonds that characterize the Middle Orange River region.

This is also a strong validation of our strategy to grow our alluvial production volumes to 500,000m3 per month in order to produce large stones more regularly and improve Rockwell's quarterly earnings performance."