Worlds Topest Jewellery Information

The Millennium Star is internally and externally flawless pear-shaped diamond (total of 54 facets). With the weight of 203.04 carats it is the 10th largest diamond in the world. Originally, the rough stone was 777 carats found in the Mbuji-Mayi district of Zaire (Democratic Republic of the Congo) in 1990. After 5 months of studying and planning the cutting of the stone, it was decided to cut the rough diamond into three pieces. The Millennium Star is the outcome of the largest piece. The value of the stone hasn't been revealed but the Millennium Star was insured for 100 million English pounds, this is believed to be a fraction of its true worth.

9. The Red Cross, Weight: 205.07 carats

The Red Cross is canary yellow cushion-shaped diamond with weight of 205.07 carats. The rough stone weighed 375 carats and was found in Kimberly mines (South Africa) in 1901. The diamond was presented as a gift to the art sale held in London by Christies in 1918, on behalf of the British Red Cross Society and the Order of St. John. Another rare feature is that a Maltese Cross is distinctly visible in the top facet, hence the double appropriateness of its name, the Red Cross Diamond.

8. The De Beers - Weight: 234.65 carats

The De Beers diamond was found in Kimberly mines in 1888, the rough stone weighed 428.50 carats and measured 47.6 mm through its longest axis and 38.1 mm square. Weighing 234.65 carats, the De Beers is the 8th largest faceted diamond in the world. After its display in Paris the Maharaja of Patiala bought the De Beers. In 1928 Cartier of Paris set it as the centerpiece of a ceremonial necklace that came to be known as the Patiala Necklace. The necklace originally contained about 2,930 diamonds weighing about 962.25 carats. Today's whereabouts of the De Beers diamond and the Patiala Nacklace is unknown.

7. The Jubilee - Weight: 245.35 carats

The Jubilee is a colorless cushion-shaped diamond with a weight of 245.35 carats. The original rough stone, an irregular octahedron without definite faces or shape weighed 650.80 carats and was found in the Jagersfontein Mine towards the end of 1895. When during the cutting it became evident that a superb diamond of exceptional purity and size was being produced, it was planned to present it to Queen Victoria. In the end this did not happen and the diamond remained with its owners. The following year marked the Diamond Jubilee of Queen Victoria (the 75th anniversary of her coronation) so the gem was renamed the Jubilee to commemorate the occasion.

6. The Centenary - Weight: 273.85 carats

The Centenary was found in Premier mine in 1986, in its rough form it weighed 599 carats. When cutting was completed the Centenary weighed 273.85 carats, measured 39.90 � 50.50 � 24.55 mm, and had 247 facets - 164 on the stone and 83 around its girdle. Never before had such a high number of facets been polished onto a diamond. The true value of the Centenary diamond is unknown, but the diamond was insured for around $100 million in 1991.

5. The Spirit of de Grisogono - Weight: 312.24

The Spirit of de Grisogono, at 312.24 carats, is the world's largest cut black diamond, and world's 5th largest diamond. In a white gold mounting, it is set with 702 white diamonds totaling 36.69 carats. This diamond originally had a rough weight of 587 carats and was mined several decades ago in west Central Africa before being imported into Switzerland.

4. The Cullinan II - Weight: 317.40 carats

The Cullinan II is the massive 317.40 carat cushion shaped diamond in the center-front of the Imperial State Crown of Great Britain. Cullinan II was cut from the largest gem-quality diamond ever found, it weighed 3106 carats, or about 1 1/3 pounds. It was named after Sir Thomas Cullinan, who opened the mine and was visiting on that eventful day. The nine larger stones of the Cullinan diamond remain either in the British Crown Jewels or in the personal possession of the Royal Family.

3. The Incomparable - Weight: 407.48 carats

The traditional classification in the West, which goes back to the Ancient Greeks, begins with a distinction between precious and semi-precious stones; similar distinctions are made in other cultures. The precious stones are diamond, ruby, emerald and sapphire, with all other gemstones being semi-precious.[2] This distinction is unscientific and reflects the rarity of the respective stones in ancient times, as well as their quality - all are translucent with fine color in their purest forms, except for the colorless diamond, and very hard,[3] with hardnesses of 8-10 on the Mohs scale. Other stones are classified by their color, translucency and hardness. The traditional distinction does not necessarily reflect modern values, for example, while garnets are relatively inexpensive, a green garnet called Tsavorite, can be far more valuable than an mid-quality emerald.[4] Another unscientific term for semi-precious gemstones used in art history and archaeology is hardstone.

In modern times gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al2O3). Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in. For example diamonds, which have a cubic crystal system, are often found as octahedrons.

Gemstones are classified into different groups, species, and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Emerald (green), aquamarine (blue), bixbite (red), goshenite (colorless), heliodor (yellow), and morganite (pink) are all varieties of the mineral species beryl.

Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and luster. They may exhibit pleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum.

Material or flaws within a stone may be present as inclusions.

Color is the most obvious and attractive feature of gemstones. The color of any material is due to the nature of light itself. Daylight, often called white light, is actually a mixture of different colors of light. When light passes through a material, some of the light may be absorbed, while the rest passes through. The part that is not absorbed reaches the eye as white light minus the absorbed colors. A ruby appears red because it absorbs all the other colors of white light - blue, yellow, green, etc. - except red.

The same material can exhibit different colors. For example ruby and sapphire have the same chemical composition (both are corundum) but exhibit different colors. Even the same gemstone can occur in many different colors: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colors from yellow to orange-pink, the latter called "Padparadscha sapphire".

This difference in color is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition, they are not exactly the same. Every now and then an atom is replaced by a completely different atom (and this could be as few as one in a million atoms). These so called impurities are sufficient to absorb certain colors and leave the other colors unaffected.

As an example: beryl, which is colorless in its pure mineral form, becomes emerald with chromium impurities. If you add manganese instead of chromium, beryl becomes pink morganite. With iron, it becomes aquamarine.

Some gemstone treatments make use of the fact that these impurities can be "manipulated", thus changing the color of the gem.

Info Taken from Wikipedia.com

Credits to wikipedia.com