Sapphire

The name sapphire ( Greek-blue) used to be applied to various stones. In antiquity and as late as the Middle Ages, the name sapphire was understood to mean what is today described as lapis lazuli. Around 1800 it was recognized that sapphire and ruby are gem varieties of corundum. At first only the blue variety was call sapphire, and corundum of other colors ( with the exception of red) were given special, misleading names, such as "Oriental peridot" for the green variety and "Original topaz" for yellow type.

Today corundum of gemstone quality of colors except red are called sapphire. Red varieties are called rubies are call rubies. The various colorless sapphire qualified by description, e.g., green sapphire or yellow sapphire . Colorless sapphire is called leuko-sapphire ( Greek-white), pinkish orange sapphire Padparadsha (Sinhalese for ''Lotus Flower'').

There is no definite demarcation between ruby and sapphire. Light red, pink, or violet corundum are usually called sapphire, as in this way they have individual values in comparison with other colors. If they were grouped as rubies, they would be stones of inferior quality. The coloring agents in blue sapphire are iron and titanium; and in violet stones, vanadium. A small iron content results in yellow and green tones; chromium produces pink, iron, and vanadium orange tones. The most desired color is a pure cornflower-blue. In artificial incandescent light, some sapphires can appear to be ink-color or black -blue.

Through heat treatment at temperatures of about 3100-3300 degree F (1700-1800 degree C), some cloudy sapphire, non distinct in color, can change to a bright blue permanent color.
Hardness is the same as ruby and also differs clearly in different directions ( an important factor in cutting). There is no fluorescence for all sapphires.
Inclusion of rutile needles result in a silky shine; oriented, i.e., aligned, needles cause a six-ray star sapphire .

Famous Rubies

Ruby is one of the most expensive gems, large rubies being rarer than comparable diamonds. The largest cuttable ruby weighted 400ct; it was found in Burma and divided into three parts. Famous stones of exceptional beauty are the Ewardes ruby (167ct) in the British Museum of Natural History in London, the Rosser Reeves star ruby (138ct) in the Smithsonian Institution in Washinton, D.C., the De Long star (100ct) in the American Museum of Natural History in New York, and the Peace ruby (43ct), thus called because it was found in 1919 at the end of World War I.
Many rubies comprise important parts of royal insignia and other famous jewelry. The Bohemian St. Wenzel's crown (Prague), for instance, holds a non faceted ruby of about 250ct. But some gems , thought to be rubies, have been revealed as spiniels, such as the ''Black Princes's ruby'' in the English State Crown and the ''Timur Ruby'' in a necklace among the English crown jewels. The drop- shaped spinels in the crown of the Wittelsbachs dating from 1830 were also originally thought to be rubies.

                                                                    Black Princes's ruby
Today rubies were cut in the countries where they were found. Because the cutters usually aim for maximum weight, the proportions are not always satisfactory, so that many stones have to be recut by dealers in other countries. Transparent qualities are cut in step and brilliant cut; less transparent stones, en cabochon or they are formed to carving. Only synthetic rubies are used for watches and bearings, formerly the most important technical application for natural stones.
Possibility for confusion with almadite, pyrope, spinel, topaz, tourmaline, and zircon. Since the beginning of the 20th century, there have been synthetic rubies with gemstone quality; these resemble natural ones especially in their chemical, physical, and optical properties. But most of them can be recognized by their inclusions as well as by the fact that they. in contrast to natural rubies, transmit shortwave ultraviolet light.
Numerous imitations currently are on the market, especially glass imitations and doublets. These have a garnet crown and glass underneath. There are many false names in the trade such as Balas ruby (=spinel), Cape ruby (=pyrope), and Siberian ruby (= tourmaline).

Deposit of Ruby

The host rocks of ruby are metamorphic dolomite marbles, gneiss, and amphibolite. The yield of rubies from such primary deposits is not economically profitable. Rather, secondary alluvial deposits are worked. Because of its high density, ruby is normally separated through the washing of river gravels, sands, and soil, then concentrate, and finally picked out by hand.
Production methods are still as primitive as they were a hundred years ago in many location. In state-owned mines, on the other hand, the usage of machinery is not exactly the rule, but much more frequent than in private companies. Some state regulated companies (e-g., Mogok in Myanmar) lately even work with highly mechanized machinery both above-and underground.
                                     
                                                            Mogok in Myanmar

                                                                   Rubies from Burma

Some of the most important deposits are in Myanmar, Thailand, Sri Lanka, and Tanzania. For centuries, the most important have been in upper Myanmar near Mogok. The ruby-bearing layer runs several yards under the surface. Apparently pigeon's blood color. They are consider to be the most valuable rubies of all. Large stones are rare. Mineral found together with ruby, often also of gemstone quality, are precious beryl, chrysoberyl, garnet, moonstone, sapphire, spinel, topaz, tourmaline, and zircon. In the early 1990s large new deposits were discovered at Mong Hsu in Myanmar. Rubies from Thailand often have a brown or violet tint to them.They are found southeast of Bangkok in the district of Chantaburi in clayey gravels. Shafts are sunk to a depth of 20 ft (8 m). However, in recent years Thai ruby production has been declining.
In Sri Lanka deposits are situated in the southwest of the island in the district of Ratnapura. Rubies from these deposits( called illam by the local population) are usually light red to raspberry-red. Some of the rubies are recovered from the river sands and gravels.
Since the 1950s Tanzania has produced a decorative green rock, a zoisite(anyolite), with the most opaque rubies. Only a few crystals are cuttable, most being used as decorative stones. On the upper Umba River(northwest Tanzania), on the other hand, rubies with gemstone quality have been found that are violet to brown-red.
Other mining deposits are in Afghanistan, Australia (Queensland, New South Wale), Brazil, Indian, Cambodia, Kenya, Madagascar, Malawi, Nepal, Pakistan, Zimbabwe, Tajikistan, the Unite States ( Montana, North Carolina), and Vietnam.
Small ruby deposits can also be found in Switzerland (Tessin), in Norway, and the southwest Coast of Greenland.

                                                        Ruby's deposit in Cambodia

 

Ruby

Ruby is thus named because of its res color(Latin-ruber). It was not until about 1800 that ruby, as well as sapphire, was recognized as belonging to the corundum species. Before that date, red spinel and the red garnet were also designated as ruby.
The red color varies within each individual deposit, so it is not possible to determine the source area from the color. The designations ''Burma ruby'' and ''Siam ruby'' are therefore strictly erroneous, and refer more to quality that origin. The most desirable color is the so-called ''pigeon's blood,'' pure red with a hint of blue.
The distribution of color is often uneven, in stripes or spots. The substance that provides thee color is chromium, and in the case of brownish tones, iron is present as well. As a rough stone, ruby appears dull and greasy, but, when cut, the luster can approach that of diamond. Heat treatment is commonly used to improve the color.
Ruby is the hardest mineral after diamond. However, the hardness varies in different directions. Ruby has no cleavage, but has certain preferred directions of parting. Because of brittleness, care must be taken when cutting and setting.
Inclusion are common. They are not always indicative of lower quality, but show the different between a natural and a synthetic stone. The type of inclusion (minerals, growth structures, canals, or other cavities) often indicates the source area.
Included rutile needle bring about either soft sheen (call silk) or, when cut en cabochon , the rare cat's eye effect, or more often the very desirable asterism-a six -rayed star, which shimmers over the surface of the stone when it is moved. Nowadays there are also Trapiche Rubies on the market. Their appearance is equal to the Trapiche Emeralds.

        Natural Ruby from Cambodia