B2S4: Durability

Question 1

Name 3 types of durability.

Answer 1

Hardness
Toughness
Stability

Question 2

What is ‘hardness’?

Answer 2

The ability of a material to resist abrasion/scratching when a pointed fragment of another substance is drawn across it without sufficient pressure to develop cleavage or fracture.

Question 3

What is ‘toughness’?

Answer 3

The ability of a material to resist the development of fracture or cleavage through the body of the material.

Question 4

What is ‘stability’?

Answer 4

Stability is the ability of a material to resist physical or chemical alteration due to light, heat, or chemical attack.

Question 5

List the gem materials on the Moh’s Hardness Scale from 1 to 10.

Answer 5

1 - Talc
2 - Gypsum
3 - Calcite
4 - Fluorite
5 - Apatite
6 - Orthoclase Feldspar
7 - Quartz
8 - Topaz
9 - Corundum
10 - Diamond

Question 6

Names 2 types of fractures.

Answer 6

Conchoidal
Hackly

Question 7

What is a ‘hackly’ fracture? Give 2 examples.

Answer 7

The uneven and often jagged surface that occurs when a material is fractured. This texture typically occurs in fractures through tough materials composed of intergrown fibrous crystals.

Example: nephrite jade

Question 8

What is a ‘conchoidal fracture’? Give 2 examples.

Answer 8

A broken surface with concentric, raised surface markings looking similar to the ridges on a seashell.

Example: obsidian, quartz

Question 9

Which 4 gems have perfect cleavage?

Answer 9

Diamond
Fluorite
Calcite
Topaz

Question 10

Define ‘cleavage’.

Answer 10

The ability, possessed by some crystalline gem materials, to split along certain well-defined crystal structure planes to leave more or less flat cleavage faces. Diamond may be cleaved during fashioning.