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Introduction:
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Sapphire is a member of the corundum group and represents every color except red, which is called ruby. Sapphire is very hard, ranked 9 on the Mohs scale of 1-10. Its vast array of colors and durability make it an excellent choice for all types of jewelry. Many consumers are unfamiliar with the fancy-colored sapphires outside special names for particular blue sapphires, such as Ceylon and London. Yellow and pink sapphires are steadily gaining popularity and offer a unique look without sacrificing wear-ability. Sapphire is mined predominately from alluvial deposits or deposits formed by weathering. Important sources for sapphire are Australia, Burma, Sri Lanka, and Thailand. Some famous sapphires are the "Star of India" (53 ct), the "Midnight Star" (116 ct), and the "Star of Asia" (330 ct). Two of the English Crown Jewels are also sapphires. Sapphire is the September birthstone and is designated for the 23rd, 30th, and 50th wedding anniversaries. |
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History
of...
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The name sapphire is derived from the word sapphiros, which referred to lapis lazuli in Roman times. Around 1800, sapphire and ruby were recognized as the gem-quality members of the corundum group. Initially only blue sapphires carried the name sapphire, while other colors were given special names that we now classify as misnomers. For example, green sapphire was called Oriental Peridot and yellow sapphire was called Oriental Topaz. Today these stones are correctly called sapphires and they are categorized by their colors. Some especially rare and fine sapphires are given names to distinguish them. These include the Kashmir sapphire and the Padparadscha sapphire. As with any special designation, there is often confusion over the specific characteristics that allow a stone to be a member of these special ranks. While some insist on color alone, others rally that origin is crucial. Still others insist that color and stone origin must coexist for stones to receive these special classifications. In sapphire's favor, general consumers appreciate the beauty and variety the stone offers without becoming overly concerned with technicalities.
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Technical
Specifications:
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| DESCRIPTION |
| Sapphire is a member of the corundum group. |
| Chemical
Composition: |
Al2O3 |
| Appearance: |
•Transparent to opaque
•Sapphire occurs in every color of the rainbow except red, which is ruby.
•May demonstrate asterism--star sapphire; color-change and chatoyancy may also occur but are more rare |
| Misnomers: |
•Yellow: Oriental topaz, king topaz, imperial topaz
•Green: Oriental emerald
•Purple: Oriental amethyst |
| Typical
Sizes: |
Melee sizes to 5 ct; faceted stones of several hundred cararts 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: |
• Purple/violet: strong violet and orange
•Green: strong green and yellow-green
•Yellow: weak yellow and light yellow
•Orange: strong yellow-brown or orange and colorless |
| Ultraviolet
Fluorescence: |
•Pink: strong orange-red (LW), weak orangy-red (SW)
•Orange: usually inert, may be strong orange-red (LW)
•Yellow: inert to moderate orange-red to orange-yellow (LW), weak red to yellow-orange (SW)
•Green: inert
•Violet and color change: inert to moderate to strong red (LW), weaker (SW)
•Colorless: inert to moderate red to orange (LW and SW)
•Brown: usually inert, may be weak red (LW and SW)
•Black: inert |
| Absorption
Spectra: |
• Green: 450, 460, 470 nm
•Yellow (Australian): 450, 460, 470 nm
•Orangy-yellow from Australia and yellow stones from other sources: no typical spectra
•Purple: may show a combination of the ruby and sapphire spectra |
| Cause
of Color: |
• Green: iron, or iron and titanium
•Yellow (stable): iron
•Yellow (fading): unstable color centers
•Orange: iron or color centers; also traces of chromium in padparadscha
•Purple: varying traces and combinations of iron, titanium, and chromium
•Pink: chromium; possibly titanium
•Color change: combined presence of chromium, vanadium, iron, and titanium |
| Specific
Gravity: |
4.0 (+.10, -.05) |
| Polish
Luster: |
Vitreous to subadamantine |
| Fracture: |
Conchoidal |
| 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 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. It is occasionally used with blue sapphires to produce a darker surface color. The treatment is stable and can be detected by immersion and magnification.
• Colorless and very light yellow sapphires are commonly heated to produce or intensify yellow, brownish, and orangy yellow tones. If a stone shows inert fluorescence and no absorption lines, it has probably been heat treated. The treatment is stable and does not require special care.
•Very dark blue and green sapphires are commonly heat treated to lighten their color.The treatment is stable and can be detected under magnification.
•Irradiation is occasionally used to produce yellow or orange stones from colorless, light yellow, and some very light blue stones. The change is unstable and will fade in minutes to days.
•Coating a sapphire with a thin film can deepen or change its color. This enhancement is rare. It can be detected under magnification and the coating will eventually wear off. |
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| DURABILITY RATINGS |
| Hardness: |
9 |
| Toughness: |
Excellent, except in repeatedly twinned or fractured stones |
| Sapphire is sometimes mistaken for: benitoite, cordierite, indicolite, kyanite, spinel, tanzanite, topaz and zircon |
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Care
Tips:
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| Cleaning Methods |
| •Ultrasonic: |
Usually safe |
| •Steamer: |
Usually safe |
| •Warm
soapy water: |
Safe |
| Stability of Stone |
| •Heat
tolerance: |
Sometimes improves color; may cause loss of color |
| •Light
tolerance: |
Stable, except for irradiated yellow and orange sapphires |
| •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
- Sapphires really have no limits to their usability and a ring is no exception. Sapphire is generally considered the best option for colored jewelry based on its cost, flexibility and durability. Blue sapphires are staple items in any jewelry box because they go with just about anything. A blue sapphire ring should be the first addition to your collection right next to your diamond ring. Sapphire are not susceptible to the hazards that will harm other colored stones. Sapphire rings are some of the most beautiful pieces of jewelry available. Earrings
- What is a sapphire ring without a matching pair of earrings? Sapphire earrings will stand the test of time and become a favorite for any jewelry lover. Availability, affordability, durability and flexibility - what more could you ask for in a piece of jewelry?
Pendants - Although the larger sizes are mostly available in blue sapphire, it is recommended that all colors available in sapphire would make for a nice pendant. Sapphires are not a difficult stone to obtain and there wide range of choices provide a great source for fine quality jewelry.
Bracelet - To match a large quantity of sapphires is a daunting task but not impossible. If a bracelet is desired and requires multiple stones then it is quite possible in sapphires. Generally, sticking to the blue variety will bring more luck than trying for the fancy colors. Sapphires are affordable and durable and pose no problem for bracelet settings.
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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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