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Introduction:
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Blue zircon, the December birthstone, is a member of the vast mineral species zircon, which can be found in a veritable rainbow of colors. Blue zircon has a limited availability-- most pieces 5 carats or larger come from jewelry from the Victorian era. Many blue zircon sales are attributed to repairing and replacing stones in estate jewelry. An interesting fact about zircon is that it has its own cut. The zircon cut is a modified round brilliant cut with an extra set of facets around the cutlet. Without a doubt, it was designed to show off the stone's high refractive index and intensive fire. Step cutting and emerald cutting are also popular with zircon. Nearly all colorless and blue zircons have been heat treated. It is important to inform customers that this practice, though usually stable, causes an already fragile stone to abrade even more easily.When selling zircon to customers, inform them of zircon's fragility and tendancy to abrade. Recommend that the stone is best protected in brooches, pendants and earrings. |
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History
of...
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Before cubic zirconia in the 1970's, colorless zircon was a popular substitute for diamond. In fact, it was sometimes sold under the misnomer "Matura Diamond" in an attempt to disguise its true status as a different mineral all together. During the 1880's, blue zircon became very popular with the Victorians and was used extensively in jewelry. Other than blue, gold and colorless zircons have been the main colors used in jewelry. In the 19th century, George Kunz proposed that Tiffany's market blue zircon under the trade name starlite. He appreciated the brilliance of the stone and thought it worth the promotion effort. While the name starlite was short-lived, blue zircon has maintained its place as the most popular zircon for use in jewelry.
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Technical
Specifications:
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| DESCRIPTION |
| Zircon is a mineral species. |
| Chemical
Composition: |
ZrSiO4 |
| Appearance: |
Zircon is a transparent material in a range of colors: colorless, blue, yellow, green, brown, orange, red and occasionally purple. |
| Misnomers: |
Matara diamond & Ceylon diamond are misnomers for colorless zircon and Siam aquamarine is an improper name for blue zircon. |
| Typical
Sizes: |
Blue & Green: 1-9 carats; faceted stones over 100 ct are known ?Orange & Yellow: 1-4 carats; faceted stones over 100 ct are known ?Red: Under 3 carats; faceted stones over 10 ct are know |
| Cut Styles: |
Faceted (Zircon cut is a modified round brilliant cut with a set of additional facets around the cutlet.) |
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| IDENTIFICATION |
| Optic
Character: |
DR, uniaxial positive, some of the low type is virtually SR |
| Refractive
Index: |
High type: 1.925-1.984 (+/- .040) ?Medium type: 1.875-1.905 (+/- .030) ?Low type: 1.810-1.815 (+/- .030--very rare under 1.80) |
| Birefingence: |
.000 to .059; low type has none to little and high type has high birefringence |
| Dispersion: |
.038 |
| Pleochroism: |
Blue: Strong blue and brownish yellow to colorless
?Green: Very weak green and yellow-green
?Orange & Brown: Weak to moderate purplish brown and brownish yellow
?Red: Moderate reddish purple and purplish brown |
| Ultraviolet
Fluorescence: |
Red to Orange-Red: Inert to strong yellow to orange (SW)
?Yellow to Orange-Yellow: Inert to moderate yellow to orange (LW and SW)
?Green: Generally inert
?Blue: Inert to moderate light blue (LW)
?Brown: Inert to very weak red (SW) |
| Absorption
Spectra: |
Some green stones may show forty or more absorption lines and bands, while some red and brown stones show none; some blue and colorless stoens show a 653.5 nm line only; low-type often shows only a broad, vague line in the 653.5 nm area. |
| Cause
of Color: |
Various color centers |
| Specific
Gravity: |
Varies from 3.90 to 4.73 (gradual increase from low to high type) |
| Polish
Luster: |
Adamantine to vitreous |
| Fracture: |
Conchoidal |
| Luster: |
Vitreous to subadamantine |
| Cleavage: |
None |
| Indentifying
Characteristics: |
•Some blue and many colorless stones will have minute, white cottony inclusions.
•Low type green stones usually shows very strong repeated twinning or zoning that may impart a milky appearance at some angles of illumination; Skeletal, angular inclusions are common |
| Known
Enhancements: |
Almost all colorless and blue zircons on the market have been heat treated to make them their most desirable color. The treatment is undetectable and generally stable. Sometimes exposure to light will revert color. |
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| DURABILITY RATINGS |
| Hardness: |
6 (low type) to 7 1/2 (high type) |
| Toughness: |
Heat-treated stones are poor to fair; Untreated stones are fair to good |
| Blue Zircon is sometimes mistaken for: Aquamarine, chrysoberyl, demantoid, diamond, hessonite, sapphire, sinhalite, topaz, tourmaline and vesuvian |
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Care
Tips:
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| Cleaning Methods |
| •Ultrasonic: |
Risky |
| •Steamer: |
Risky |
| •Warm
soapy water: |
Risky |
| Stability of Stone |
| •Heat
tolerance: |
High and medium types may change to colorless, blue, yellow or red under exposure to heat. |
| •Light
tolerance: |
Some heat treated stones will revert in color under exposure to light. |
| •Chemical tolerance: |
None |
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Recommended
Uses:
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Rings
- Using blue zircon in a ring is not the safest use of the stone but for the careful ring owner may be considered. The stones low tolerance for abuse, heat and light exposure makes for poor use in a ring that may be worn extensively. Blue zircon makes for a beatiful center stone set in white metal. The piece would be best used for occassional wear such as a nice dinner out with friends. Earrings
- The affordability of the stone and the availability of average sized pieces makes blue zircon a great choice for earrings. The lack of abuse earrings will recieve is another great reason to consider blue zircon for earrings. If considering larger sized stones for earrings then finding a matched set may be a bit difficult but not impossible. Match a pair of medium to small sized rounds with a pendant for a unique and beautiful set of jewelry.
Pendants - Although larger sized stones are somewhat difficult to obtain, blue zircon is well suited for a pendant. Take great care though because the stone is delicate enough that the occassional banging around of a pendant may abrade the stone. It is best suited for a shorter chain to minimize the amount of abuse a pendant may take. Affordability and beauty are the key reasons why a blue zircon works well in this application. Don't forget the brooch!
Bracelet - Because average sized stones are available at an affordable price, blue zircon may be a consideration for a bracelet but not recommended. Given the fragile nature of the stone and regular abuse a bracelet takes blue zircon is not suited for this application.
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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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