The Diamond Crystal (Chapter 7, Key Terms & Key Concept)

Question 1

A solid mass of individual, randomly
oriented crystals, intergrown or held together by a
natural binding agent.

Answer 1

Aggregate

Question 2

Plane parallel to a possible crystal
face, where a diamond can split cleanly when struck.

Answer 2

Cleavage plane

Question 3

A chemical bond formed by two
atoms sharing electrons.

Answer 3

Covalent bond

Question 4

Solid matter with atoms arranged in a
regular, repeating pattern

Answer 4

Crystal

Question 5

Composed of crystals or related to
crystals.

Answer 5

Crystalline

Question 6

Internal directions parallel to a
mineral’s unit cell surfaces.

Answer 6

Crystal planes

Question 7

Geometric shape of a
well-formed crystal.

Answer 7

Crystal shape (form)

Question 8

Regular, repeating
arrangement of atoms in a mineral.

Answer 8

Crystal structure (lattice)

Question 9

Categories of crystals based on
their symmetry and internal structure.

Answer 9

Crystal systems

Question 10

The appearance of double images of a
gemstone’s facet junctions on the side opposite the
viewer.

Answer 10

Doubling

Question 11

Possessing different
physical or optical properties in different crystal
directions.

Answer 11

Doubly refractive (anisotropic)

Question 12

A well-shaped, transparent, octahedral
diamond crystal with sharp, square edges.

Answer 12

Glassie

Question 13

Crystal distortion caused during growth
when one part of the lattice is offset in relation to
the res

Answer 13

Glide plane

Question 14

Visible, shadow-like lines in
a diamond caused by irregularities in the crystal
structure.

Answer 14

Graining (grain lines)

Question 15

Characteristic crystal shape of a specific
mineral.

Answer 15

Habit

Question 16

A flat, triangular twinned diamond crystal.

Answer 16

Macle

Question 17

A form with eight equal triangular faces

Answer 17

Octahedron

Question 18

Possessing the same
physical or optical properties in all crystal directions.

Answer 18

Singly refractive (isotropic)

Question 19

Ratio of the weight of a
material to that of an equal volume of water.

Answer 19

Specific gravity (SG)

Question 20

In diamond, a group of five carbon
atoms with one at the center

Answer 20

Tetrahedron

Question 21

The relative ability of a
material to transfer heat.

Answer 21

Thermal conductivity

Question 22

Capacity of a material to
expand when it’s heated

Answer 22

Thermal expansion

Question 23

Atoms in a gem that aren’t part of
its essential chemical composition.

Answer 23

Trace elements

Question 24

Crystal consisting of two or more
intergrown crystals with opposing crystal directions.

Answer 24

Twinned crystal

Question 25

Smallest group of atoms with the characteristic chemical composition and the basic crystal structure of a mineral.

Answer 25

Unit cell

Question 26

Covalent bonds are the strongest of all atomic bonds.

Answer 26

Key Concepts

Question 27

Diamond’s atoms are more closely bonded than the atoms of any other natural material.

Answer 27

Key Concept

Question 28

The most common habit of gem diamond is the octahedron, but perfectly shaped octahedral rough is rare.

Answer 28

Key Concept

Question 29

Diamonds belong to the cubic or isometric crystal system, the most symmetrical of the crystal systems.

Answer 29

Key Concept

Question 30

Shape is the most important factor in a rough gem diamond crystal’s potential value.

Answer 30

Key Concept

Question 31

Cubic planes provide the most efficient sawing directions for dividing large, regularly shaped crystals.

Answer 31

Key Concept

Question 32

The macle is the most common twinned diamond crystal.

Answer 32

Key Concept

Question 33

Diamond rough’s potential as a faceted gem depends on its shape, clarity, and color.

Answer 33

Key Concept

Question 34

Inclusions can limit a rough diamond’s potential shape.

Answer 34

Key Concept

Question 35

The cubic, octahedral, and dodecahedral planes are the most important directions to a diamond cutter.

Answer 35

Key Concept

Question 36

A flat, triangular twinned diamond crystal is called a

Answer 36

macle.

Question 37

The smallest group of atoms with a characteristic chemical composition and the basic crystal structure of a mineral is called a(n)

Answer 37

unit cell.

Question 38

The diamond term glassie refers to

Answer 38

a well-formed octahedral crystal.

Question 39

Another name for the cubic crystal system is

Answer 39

isometric.

Question 40

Atoms in a gem that aren’t part of its essential chemical composition are called

Answer 40

trace elements.

Question 41

Solid matter with atoms arranged in a regular, repeating pattern is called a(n)

Answer 41

crystal.

Question 42

Squares or rectangles, trigons, and parallel grooves are types of

Answer 42

growth marks.

Question 43

A naturally occurring, inorganic substance with a characteristic chemical composition and usually a characteristic crystal structure is known as a

Answer 43

mineral.

Question 44

The crystal planes most suitable for cleaving a diamond are the

Answer 44

octahedral planes.

Question 45

In diamonds, cleavage is caused by

Answer 45

relatively wide spaces between some atomic planes.

Question 46

Crystal shape is an important factor in the evaluation of rough because

Answer 46

it affects the amount of weight retained after cutting.

Question 47

Which is the softest crystal direction in diamond?

Answer 47

Dodecahedral

Question 48

What is the specific gravity of gem-quality diamond?

Answer 48

3.52

Question 49

The habit of gem-quality diamond is the

Answer 49

octahedron.

Question 50

The strongest of all atomic bonds are called

Answer 50

covalent.