Gems and Their Physical Properties- AS 3 KT

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Questions and Answers

What is the term for a gemstone's ability to resist scratches and abrasion?

Density

Stability

Durability

Hardness (correct)

What is the term for a flat break in a gemstone caused by concentrated included minerals parallel to a twinning plane?

Parting (correct)

Cleavage

Conchoidal fracture

Fracture

What is the term for a hollow cavity in a gem filled with a liquid, a gas, and one or more crystals?

Cryptocrystalline

Microcrystalline

Liquid inclusion

Three-phase inclusion (correct)

What is the term for an aggregate made up of individual crystals detectable only under very high magnification?

Cryptocrystalline Signup and view all the answers

What is the term for damage caused by sudden, extreme temperature changes?

Thermal shock Signup and view all the answers

What is the term for a characteristic enclosed within a gemstone or reaching its surface from the interior?

Inclusion Signup and view all the answers

What is the term for the characteristic external crystal shape or form of a mineral?

Habit Signup and view all the answers

What type of fracture in a gemstone extends from the surface inward with a curved and ridged shape?

Conchoidal fracture Signup and view all the answers

What is the term for the ratio of the weight of a material to the weight of an equal volume of water?

Specific gravity Signup and view all the answers

What type of inclusion is a small pocket in a gem that’s filled with fluids and, sometimes, gas bubbles and tiny crystals?

Liquid inclusion Signup and view all the answers

What is the term for the ability of a gemstone to withstand wear, heat, and chemicals?

Durability Signup and view all the answers

What is the term for an aggregate made up of individual crystals visible under magnification?

Microcrystalline Signup and view all the answers

What is the term for a mass of tiny, randomly oriented crystals?

Aggregate Signup and view all the answers

Which of the following physical properties determines how well a gemstone resists light, heat, and chemicals?

Stability Signup and view all the answers

What is the difference between a cleavage and a parting?

Cleavage is a break caused by weak atomic bonds, while parting is a break caused by inclusions Signup and view all the answers

Which of the following is an example of a three-phase inclusion?

A hollow cavity in a gem filled with a liquid, a gas, and one or more crystals Signup and view all the answers

What is the term for a gemstone's ability to withstand scratches and abrasion?

Hardness Signup and view all the answers

What is term for a flat break caused by concentrated included minerals parallel to a twinning plane?

Parting Signup and view all the answers

What is the main factor that determines a gem's density and specific gravity?

The types of atoms it's made of Signup and view all the answers

Why are some gems rare?

Because they require rare chemical elements or unique geological conditions Signup and view all the answers

What can be affected by the presence of large inclusions in a gemstone?

The beauty, value, and durability of the gemstone Signup and view all the answers

What can be used to help identify a gemstone as natural or manmade?

The inclusions in the gemstone Signup and view all the answers

What determines how a gem reacts to external stress?

The crystal structure of the gemstone Signup and view all the answers

Why do the shapes and sizes of rough gem crystals affect the shapes and sizes of finished stones?

Because the shape of the rough gem crystal determines the shape of the finished stone Signup and view all the answers

The term for how well a gem stone resists breaking and chipping is ....

Toughness Signup and view all the answers

A change in a gems crystal direction during or after growth is....?

Twinning Signup and view all the answers

What term is used for the smallest group of atoms with both characteristic chemical composition and crystal structure of a mineral ?

Unit Cell Signup and view all the answers

What is the location of a change in crystal growth direction?

Twinning Plane Signup and view all the answers

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?

Cleavage Signup and view all the answers

A fracture is ....?

Any break in a gem other than cleavage or parting Signup and view all the answers

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.