Podcast
Questions and Answers
What is the term for a gemstone's ability to resist scratches and abrasion?
What is the term for a gemstone's ability to resist scratches and abrasion?
What is the term for a flat break in a gemstone caused by concentrated included minerals parallel to a twinning plane?
What is the term for a flat break in a gemstone caused by concentrated included minerals parallel to a twinning plane?
What is the term for a hollow cavity in a gem filled with a liquid, a gas, and one or more crystals?
What is the term for a hollow cavity in a gem filled with a liquid, a gas, and one or more crystals?
What is the term for an aggregate made up of individual crystals detectable only under very high magnification?
What is the term for an aggregate made up of individual crystals detectable only under very high magnification?
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What is the term for damage caused by sudden, extreme temperature changes?
What is the term for damage caused by sudden, extreme temperature changes?
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What is the term for a characteristic enclosed within a gemstone or reaching its surface from the interior?
What is the term for a characteristic enclosed within a gemstone or reaching its surface from the interior?
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What is the term for the characteristic external crystal shape or form of a mineral?
What is the term for the characteristic external crystal shape or form of a mineral?
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What type of fracture in a gemstone extends from the surface inward with a curved and ridged shape?
What type of fracture in a gemstone extends from the surface inward with a curved and ridged shape?
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What is the term for the ratio of the weight of a material to the weight of an equal volume of water?
What is the term for the ratio of the weight of a material to the weight of an equal volume of water?
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What type of inclusion is a small pocket in a gem that’s filled with fluids and, sometimes, gas bubbles and tiny crystals?
What type of inclusion is a small pocket in a gem that’s filled with fluids and, sometimes, gas bubbles and tiny crystals?
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What is the term for the ability of a gemstone to withstand wear, heat, and chemicals?
What is the term for the ability of a gemstone to withstand wear, heat, and chemicals?
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What is the term for an aggregate made up of individual crystals visible under magnification?
What is the term for an aggregate made up of individual crystals visible under magnification?
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What is the term for a mass of tiny, randomly oriented crystals?
What is the term for a mass of tiny, randomly oriented crystals?
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Which of the following physical properties determines how well a gemstone resists light, heat, and chemicals?
Which of the following physical properties determines how well a gemstone resists light, heat, and chemicals?
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What is the difference between a cleavage and a parting?
What is the difference between a cleavage and a parting?
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Which of the following is an example of a three-phase inclusion?
Which of the following is an example of a three-phase inclusion?
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What is the term for a gemstone's ability to withstand scratches and abrasion?
What is the term for a gemstone's ability to withstand scratches and abrasion?
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What is term for a flat break caused by concentrated included minerals parallel to a twinning plane?
What is term for a flat break caused by concentrated included minerals parallel to a twinning plane?
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What is the main factor that determines a gem's density and specific gravity?
What is the main factor that determines a gem's density and specific gravity?
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Why are some gems rare?
Why are some gems rare?
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What can be affected by the presence of large inclusions in a gemstone?
What can be affected by the presence of large inclusions in a gemstone?
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What can be used to help identify a gemstone as natural or manmade?
What can be used to help identify a gemstone as natural or manmade?
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What determines how a gem reacts to external stress?
What determines how a gem reacts to external stress?
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Why do the shapes and sizes of rough gem crystals affect the shapes and sizes of finished stones?
Why do the shapes and sizes of rough gem crystals affect the shapes and sizes of finished stones?
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The term for how well a gem stone resists breaking and chipping is ....
The term for how well a gem stone resists breaking and chipping is ....
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A change in a gems crystal direction during or after growth is....?
A change in a gems crystal direction during or after growth is....?
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What term is used for the smallest group of atoms with both characteristic chemical composition and crystal structure of a mineral ?
What term is used for the smallest group of atoms with both characteristic chemical composition and crystal structure of a mineral ?
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What is the location of a change in crystal growth direction?
What is the location of a change in crystal growth direction?
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What is a smooth, flat break in a gemstone parallel to planes of atomic weakness, caused by weak or fewer bonds between atoms or both?
What is a smooth, flat break in a gemstone parallel to planes of atomic weakness, caused by weak or fewer bonds between atoms or both?
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A fracture is ....?
A fracture is ....?
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Study Notes
Physical Properties of Gems
- Aggregate: A mass of tiny, randomly oriented crystals.
- Parting: A flat break in a gemstone caused by concentrated included minerals parallel to a twinning plane.
- Cleavage: A smooth, flat break in a gemstone parallel to planes of atomic weakness, caused by weak or fewer bonds between atoms, or both.
Fractures and Breaks
- Conchoidal fracture: A curved and ridged fracture in a gemstone, extending from the surface inward.
- Fracture: Any break in a gem other than cleavage or parting.
Properties of Gems
- Specific gravity (SG): Ratio of the weight of a material to the weight of an equal volume of water.
- Density: How heavy an object is in relation to its size.
- Hardness: How well a gemstone resists scratches and abrasion.
- Durability: A gemstone's ability to withstand wear, heat, and chemicals.
- Stability: How well a gemstone resists light, heat, and chemicals.
Inclusions and Structures
- Inclusion: A characteristic enclosed within a gemstone or reaching its surface from the interior.
- Liquid inclusion: Small pocket in a gem that's filled with fluids and, sometimes, gas bubbles and tiny crystals.
- Three-phase inclusion: A hollow cavity in a gem filled with a liquid, a gas, and one or more crystals.
- Cryptocrystalline: An aggregate made up of individual crystals detectable only under very high magnification.
- Microcrystalline: An aggregate made up of individual crystals visible under magnification.
Other Terms
- Habit: The characteristic external crystal shape or form of a mineral.
- Thermal shock: Damage caused by sudden, extreme temperature changes.
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Description
Test your knowledge of key terms related to gems and their physical properties, including aggregate, parting, cleavage, specific gravity, and conchoidal fracture.
