Assignment 3 - Gems and their Physical Properties Flashcards
• Describe the growth of a gem crystal. • Explain how and when inclusions become part of a gem. • Recognize the outward signs of a gem’s inner structure. • Understand the relationship between a gem’s structure and its finished shape. • Relate a gem’s physical properties to its usefulness in jewelry.
A mass of tiny, randomly
oriented crystals.
Aggregate
An aggregate made up of individual crystals visible under
magnification.
Microcrystalline
An aggregate made up of individual crystals detectable only under very high magnification.
Cryptocrystalline
Change in a gem’s crystal
direction during or after growth.
Twinning
A characteristic enclosed within a gemstone or reaching its
surface from the interior.
Inclusion
Small pocket in a gem that’s filled with fluids and, sometimes, gas bubbles and tiny crystals.
Liquid inclusion
A hollow cavity in a gem, usually filled with a liquid and a gas.
Two-phase inclusion
A hollow cavity in a gem filled with a liquid, a gas, and one or more crystals.
Three-phase inclusion
Atoms in a gem that aren’t part of its essential chemical composition.
Trace elements
The characteristic external
crystal shape or form of a mineral.
Habit
How heavy an object is in
relation to its size.
Density
Ratio of the weight of a material to the weight of an equal volume of water.
Specific gravity (SG)
A gemstone’s ability to
withstand wear, heat, and chemicals.
Durability
How well a gemstone
resists scratches and abrasion.
Hardness
How well a gemstone
resists breaking and chipping.
Toughness
A smooth, flat break in a
gemstone parallel to planes of
atomic weakness, caused by weak or fewer bonds between atoms, or both.
Cleavage