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Organic Gems (Amber (Tree resin has to harden over time
and be at least a…
Organic Gems
Amber
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- Composition: a compound of carbon, hydrogen, and oxygen, with traces of sulfur
- Amorphous, no crystal structure
- Mohs scale: 2 to 2.5
- Transparent to opaque look
Value:
- Transparent red amber > Golden amber > yellow amber
- Pieces containing insect or plant inclusions > inclusion-free pieces
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Principal Source: The Baltic Sea region & the Dominican Republic
- Baltic amber is generally more expensive than Dominican amber.
Treatment
- Heat treatment with oil --> clarity cloudy amber
- Sun spangles: circular marks sometimes left in amber when treaters heat and oil it
Imitations
Copal is probably the most common natural imitator, while Bakelite, a plastic, is probably the most prevalent artificial imitator
Coral
#1:Calcareous Coral
A chemical compound containing calcium, carbon, and oxygen—in the form of calcite
Because Italy is the most important coral-marketing center, many coral color terms are Italian.
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Cut style: beads, cabochons, carvings & cameo
- One of the most imitated organic gems
- Most Common imitations: glass, porcelain & plastics, Gilson imitation coral
#2: Conchiolin Coral
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- Black Coral comes from Queenland, Australia & Hawaii
- Golden Coral comes from Hawaii & Tasmania, Australia
- Golden coral is more rare than black coral
- As of 1994, Australia banned coral exports
- Bleaching can create a golden color from black coral
- Mohs scale: 3.5
- Semitranslucent to
opaque
Ivory
- Mohs scale: 2.25 - 2.75, fair toughness
- Nearly all trade in new elephant ivory
has been illegal since the mid-1970s.
- It's legal to trade in ivory from extinct elephant species, such as the woolly mommoths
Imitation
- Common imitations: Celluloid & Bone
- Others: Deer horn (animal source), Seed of ivory palm & Nut from doum plam's fruits (veggie source)
Shell
- Nearly all shells used today in jewelry and other ornamental pieces come from saltwater sources.
- Mohs scale: 3.5
- The most widely used cameo materials are the various members of the helmet shell species, which have layers of contrasing colors
- Shells are commonly dyed to produce a variety of colors
- Common imitations: Molded glass & plastic
How to judge quality of Cameo
- #1, the strength of color of the various layers, and their relative contrast
- #2, the quality of craving
- #3, Any surface waxing to hide pits or other defects,
Ammonite
The fossilized remains of hard-shelled,
squid-like marine mollusks that lived
between 65 million and 395 million years ago
- Size Range: Less than 1 inch to 9 ft in diameter
- Source: Canada
- Often cut into half to expose the spiral structure
- Often retain natural shape & border them in metal
- No imitators
Tortoise Shell
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- A dark amber color w/ raditing streaks of brown or black
- Mohs scale: 2.5, fairly tough
- Hawksbill turtles have been protected since 1975
Imitations: Celluloid, casein & Bakelite plastic
Jet
煤精石
- the ornamental form of light coal that formed when wooden logs washed out to sea and sank into mud on the sea floor
- Mohs scale: 2.5 to 4
- Semitranslucent to opaque
- Source: England (Major), others: Canada, France
- Imitators - Vulcanite, glass, obsidian, dyed black chalcedony and various plastics
- Jet was popular as mourning jewelry in the late Victorian era.
Many sources of organic gem materials are endangered and protected by environmental laws.
Organic gems have a natural appeal that’s enhanced by the fact that they