40 Questions
What is the typical hardness of Amber on the Mohs scale?
2 to 2.5
What is the characteristic polish luster of Amber?
resinous—to vitreous
What is the typical color range of Amber?
Transparent to opaque, including yellow, golden, white, orange-to-red, or brown
What feature of Amber increases its value?
Pieces with insect or plant inclusions
Which market has a strong demand for Amber?
Chinese market
What is the minimum age requirement for tree resin to be classified as amber?
At least a million years old
What is the main difference between copal and amber?
Copal is softer and melts at a lower temperature than amber
What is the age range of copal?
Less than a million years old
What happens to the tree resin over time to form amber or copal?
It undergoes a process of polymerization
What is the main difference between the hardness of copal and amber?
Amber is harder than copal
What is the characteristic of transparent red amber in terms of its value?
It is more valuable than golden amber
What is the primary difference between transparent red amber and golden amber?
Their transparency levels
What is the effect of strong fluorescence on the appearance of amber?
It gives amber a bluish or greenish appearance
Which type of amber is not mentioned in the passage?
Blue amber
What is the difference between copal and amber?
Copal is a type of fossilized resin
Which region in Europe is the world's leading source of Amber?
Baltic Sea region
What is the main difference between Amber and Copal?
Copal is softer than Amber
What is the second-largest producer of Amber?
Dominican Republic
What is a common shape of Amber jewelry?
Beads
What is a country where Amber is also found?
Mexico
What is a common treatment for cloudy amber?
Heating it in rapeseed oil
What is a method used to create larger pieces of amber?
Pressing small pieces or chips together under gentle heat and pressure
What is a common effect of staining amber?
Producing a green color
What is a possible result of heating amber in rapeseed oil?
Creating 'sun spangles'
What is a common reason for dyeing amber?
To make it look more aged
What is a natural imitator of Amber?
Copal
What is the most common artificial imitator of Amber?
Bakelite
What is another name for Ammonite?
Ammolite
What is the name of the imitation coral made from calcite and silica?
Gilson
What is the name of the Maori name for Abalone Shell?
Paua
What type of material is often used to make imitations of coral?
All of the above
What is the name of the type of coral also known as 'King' or 'Akabar coral'?
Black coral
What is the name of the type of coral also known as 'oxblood'?
Red coral
What is the name of the type of coral also known as 'pelle d'angelo'?
Pink coral
What is the name of the type of coral also known as 'salmon'?
Vivid pink coral
What can cause amber to change its color?
Oxidation
What is commonly found embedded in amber?
Flower parts, leaves, pine needles, and insects
What is a characteristic of Moldavite?
It has few or no included bubbles and can be spherical or flattened
What is the name of the massive crystalline variety of fluorite?
Derbyshire spar
What was obsidian used for in prehistoric times?
Fashioning spear points, knives, and tools
Study Notes
Organics and Collectors' Stones
- Amber:
- High demand from China
- Pieces with insect or plant inclusions are more valuable
- Soft, with a hardness of 2 to 2.5 on the Mohs scale
- Can be transparent to opaque, with a resinous to vitreous luster
- Colors include yellow, golden, orange, red, brown, and white
- Formed from hardened tree resin, at least a million years old
- Coral:
- High demand from China
- Types include calcareous coral and conchiolin coral
- Semi-translucent to opaque, with a waxy to vitreous luster
- Colors include white, cream, pink, red, orange, blue, purple, and lavender
- Formed from the skeletal remains of tiny marine-animal colonies
- Moldavite:
- Highly prized in the Chinese market
- Hardness of 5 to 6 on the Mohs scale
- Transparent to translucent, with a vitreous luster
- Colors include green, brown, and rarely, blue or purple
- Formed from meteorite impact
- Ivory:
- High demand from China
- Soft, with a hardness of 2.25 to 2.75 on the Mohs scale
- Polish luster is greasy to dull
- Colors include white, light yellow, and translucent to opaque
- Formed from elephant tusks
- Shell:
- Types include mother-of-pearl, abalone, helmet shell, and queen conch shell
- Colors include white, pink, orange, yellow, green, brown, and blue
- Formed from the shells of marine mollusks
- Jet:
- Formed from lignite coal
- Black, with a hardness of 2.5 to 4 on the Mohs scale
- Used in mourning jewelry in the Victorian era
- Benitoite:
- Rare, with a hardness of 6.5 on the Mohs scale
- Colors include blue, white, and rarely, red
- Formed from the mineral benitoite
- Fluorite:
- Low hardness, with a Mohs scale rating of 5
- Colors include black, blue, green, yellow, orange, and purple
- Formed from hydrothermal activity
- Kyanite:
- Hardness varies depending on direction, 7 across the crystal and 5 along its length
- Colors include blue, white, and rarely, green
- Formed from high-pressure metamorphism
- Sphene:
- Low hardness, with a Mohs scale rating of 5
- Colors include yellow, green, brown, orange, and rarely, red
- Formed from hydrothermal activity
- Tortoise Shell:
- Formed from the shells of Atlantic hawksbill sea turtles
- Colors include brown, yellow, orange, and red
- Used in jewelry and decorative objects
- Ammonite:
- Fossilized remains of hard-shelled, squid-like marine mollusks
- Colors include brown, yellow, orange, and red
- Formed from the fossilization of ammonites
Mohs Scale
- Apatite: 5
- Benitoite: 6.5
- Coral: 3.5
- Fluorite: 5
- Ivory: 2.25 to 2.75
- Jet: 2.5 to 4
- Kyanite: 7 across the crystal, 5 along its length
- Moldavite: 5 to 6
- Obsidian: 5 to 5.5
- Shell: 3.5
- Sphene: 5
- Tortoise Shell: 2.5, fairly tough
Color and Luster
- Amber: resinous to vitreous luster
- Coral: waxy to vitreous luster
- Ivory: greasy to dull luster
- Jet: vitreous luster
- Moldavite: vitreous luster
- Obsidian: resinous to vitreous luster
- Shell: greasy or pearly luster
- Tortoise Shell: resinous to vitreous luster
Test your knowledge of rocks and minerals, including obsidian, sphene, and amber, and their distinct characteristics such as color, transparency, and formation.
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