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Introduction:
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Ruby is the most valuable member of the corundum group, which also contains sapphire. While rubies and sapphires share a chemical composition, the materials that give ruby its color occur less frequently than those that give color to sapphire, therefore, ruby is more rare. Some large, fine quality rubies are more valuable than comparable diamonds. There are no specific rules for differentiating a pink sapphire from a ruby. Rather, it just makes sense to market lighter stones as fancy pink sapphires as opposed to lower quality rubies. Ruby is taken from alluvial deposits because mining its primary sources is not economical. Some government-owned mines use machinery, but most ruby is collected in a primitive fashion by washing river gravel and sand and then picking the valuable material out by hand. The July birthstone is one of the most popular gemstones and is designated for the 40th wedding anniversary. |
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History
of...
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In ancient times and through the Middle Ages, the word ruby was used to refer to all red gemstones. No distinction was made between ruby, pyrope, spinel, and almandine. In fact, many famous rubies from assorted European royal jewelry have since been recognized as spinels. Some of these are the Timur Ruby and the Black Prince's Ruby. In 1800, the word ruby was assigned to red, gem-quality corundum. Today rubies are often cut in the countries where they are found. Cutters in these countries focus on maintaining maximum weight, so sometimes the stones have to be recut to correct proportion problems. In the 20th, century synthetic rubies with remarkable similarities to their natural counterparts were developed. The synthetic stones can be identified by their tendancy to transmit shortwave ultraviolet light, a characteristic that natural rubies do not posses.
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Technical
Specifications:
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| DESCRIPTION |
| Ruby is a member of the corundum group. |
| Chemical
Composition: |
Al2O3 |
| Appearance: |
•Transparent to opaque
•Orangy red to purplish red, brownish red
•May demonstrate asterism--star ruby; chatoyancy may also occur but this phenomena is very rare |
| Misnomers: |
None known |
| Typical
Sizes: |
Melee sizes to 5 ct; faceted stones exceeding 100 carats occur |
| Cut Styles: |
Faceted, cabochons |
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| IDENTIFICATION |
| Optic
Character: |
DR, uniaxial negative |
| Refractive
Index: |
1.762-1.770 (+.009, -.005) |
| Birefingence: |
.008 to .010 |
| Dispersion: |
.018 |
| Pleochroism: |
Strong purplish red and orangy red |
| Ultraviolet
Fluorescence: |
•Burma: strong red (LW), moderate red (SW)
•Ceylon: strong orange-red (LW), moderate orange-red (SW)
•Thai: weak red (LW), inert (SW) |
| Absorption
Spectra: |
A strong doublet at 694.2 and 692.8 nm which may appear as a fluorescent line, fairly distinct lines at 668 and 659.2 nm, broad absorption from 620 to 540 nm, a strong doublet at 476.5 and 475 nm, and general absorption of the violet |
| Cause
of Color: |
Chromium, with possible modification of color by iron and titanium |
| Specific
Gravity: |
4.0 (+/-.05) |
| Polish
Luster: |
Vitreous to subadamantine |
| Fracture: |
Conchoidal, uneven |
| Luster: |
Vitreous |
| Cleavage: |
None; twinned stones may show parting |
| Indentifying
Characteristics: |
Silk (fine needle-like rutile or boehmite crystals); rutile needles often arranged in 3 sets that intersect on another at 60° angles; zircon crystals usually surrounded by a halo of dark fractures; fingerprint inclusions, hexagonal growth lines and color zoning |
| Known
Enhancements: |
•Heating followed by controlled cooling is occasionally to commonly used to reduce rutile-clouding. This procedure can sometimes be detected under magnification. The treatment is stable unless the stone is heated above 1600°C and then slowly cooled.
• Diffusion is a process of heating the stone above 1900°C in the presence of coloring agents, such as titanium dioxide. It is occasionally used to create or improve asterism and can diffuse color to the surface of the stone. The treatment is stable and can be detected by immersion and magnification.
• Heating and slow cooling is also used occasionally to create and improve asterism. This process only works with some material. It is often undetectable and remains stable unless the stone is heated above 1600°C and cooled.
•Heating is commonly used to remove purple or brown coloring from ruby. The treatment is stable and sometimes difficult to detect.
•Some more obscure treatments include using oil and dye to hide cracks and improve the color of ruby and filling in cavitites and cracks with glass. These treatments can be detected by magnification and magnification and immersion, respectively. The oils and dyes my fade, dry out, or change colors. The glass filling can be destroyed if the stone receives knocks and bumps. |
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| DURABILITY RATINGS |
| Hardness: |
9 |
| Toughness: |
Excellent, except in repeatedly twinned or fractured stones |
| Ruby is sometimes mistaken for: almandine, fluorite, spinel, pyrope, topaz, tourmaline and zircon |
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Care
Tips:
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| Cleaning Methods |
| •Ultrasonic: |
Usually safe, but never for oiled stones |
| •Steamer: |
Usually safe, but never for oiled stones |
| •Warm
soapy water: |
Safe; avoid strong detergents and vigorous scrubbing on oiled stones |
| Stability of Stone |
| •Heat
tolerance: |
Sometimes improves color |
| •Light
tolerance: |
Stable |
| •Chemical tolerance: |
Attacked with difficulty; may lose polish if boiled in a diamond cleaning kit; smoldering flux or pickling solution containing borax will etch the surface of the stone |
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Recommended
Uses:
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Rings
- Rubies are best suited for ring settings and are considered extremely durable among colored stones. Because rings take much abuse other colored stones are not always the best choice for mounting in a ring. However, rubies work well and are a great alternative to the typical diamond ring. Center stone rubies are available and will add color and life to any fine jewelry collection. Surrounded with diamonds or by themselves rubies show character and diversity in taste for jewelry. Earrings
- Often requested are matched sets for ruby earrings. The range of red colors, sizes and shapes available in small to medium sized rubies is wide and should be considered when looking for earrings. A pair of ruby earrings is becoming a staple item for many jewelry lovers and there is almost no limit to the possibilities. Be aware that larger rubies are difficult to obtain especially in matching pairs or trios. You can't go wrong with a nice pair of ruby earrings.
Pendants - Due to economic factors, rubies are better suited for rings but a nice ruby pendant makes for a wonderful piece of fine jewelry. Generally, pendants are more popular in larger sized stones but this in no way should deter a ruby lover from adding one to their collection. They are plenty durable and will work with a wide range of fashions. Only size restrictions and cost of this precious stone should deter use in a pendant mounting.
Bracelet - Ruby bracelets are beautiful and unique. The stone will have no problem withstanding the abuse a bracelet receives. If a bracelet with multiple matching stones is required then one should consider the expense and availability of rubies. That said, a collection of nicely matched rubies mixed with diamonds would make for a phenomenal peice of jewelry. The wearer of such a fine peice should consider themselves of the elite in jewelry fashion.
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Source
Map:
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| All technical specifications and care
tips on this page was referrenced from the "Gem
Reference Guide" published by the Gemological Institute
of America |
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