key_terms_ass_5

Question 1

Aggregate

Answer 1

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

Question 2

Atom

Answer 2

The basic structural unit of all matter.

Question 3

Cleavage

Answer 3

A smooth flat break in a crystal parallel to a cleavage plane.

Question 4

Cleavage Plane

Answer 4

A planar surface along which a mineral tends to break due to atomic weakness.

Question 5

Covalent Bond

Answer 5

A chemical bond formed by two atoms sharing electrons.

Question 6

Crystal

Answer 6

Solid matter with atoms arranged in a regular repeating pattern.

Question 7

Crystal Axes

Answer 7

A reference system used to describe the symmetry and shape of crystals.

Question 8

Crystal Planes

Answer 8

Any set of parallel and evenly spaced planes distributed along certain crystal directions in which atoms are more closely packed.

Question 9

Crystal Shape (form)

Answer 9

The geometric shape of a well-formed crystal.

Question 10

Crystal Structure (lattice)

Answer 10

The regular repeating arrangement of atoms in a mineral.

Question 11

Crystal Systems

Answer 11

Categories of crystals based on their symmetry and internal structure.

Question 12

Crystalline

Answer 12

Composed of crystals or related to crystals.

Question 13

Defect

Answer 13

An imperfection or deviation from the ideal crystal lattice.

Question 14

Doubly Refractive (anisotropic)

Answer 14

Possessing different physical or optical properties in different crystal directions.

Question 15

Glassie

Answer 15

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

Question 16

Glide Plane

Answer 16

The plane or surface in which a dislocation travels through the crystal to cause an offset.

Question 17

Graining (Grain Lines)

Answer 17

Visible shadow-like lines in a diamond caused by glide planes in the crystal structure.

Question 18

Growth Marks

Answer 18

Visible features on the surface of a mineral crystal that reflect its internal growth and development.

Question 19

Habit

Answer 19

The characteristic crystal shape or form of a mineral.

Question 20

Line Defect (Dislocation)

Answer 20

Imperfection or deviation from the ideal arrangement of atoms in relation to a line in the crystal lattice.

Question 21

Macle

Answer 21

A flat triangular twinned diamond crystal.

Question 22

Octahedron

Answer 22

A crystal shape with eight equal triangular faces.

Question 23

Point Defect

Answer 23

An imperfection or deviation from the ideal arrangement of atoms in relation to a single atom or point in the crystal lattice.

Question 24

Resorption

Answer 24

The process in which the outer surface of a diamond is partially dissolved during transport.

Question 25

Singly Refractive (Isotropic)

Answer 25

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

Question 26

Specific Gravity (SG)

Answer 26

The ratio of the weight of a material to the weight of an equal volume of water.

Question 27

Spectroscopy

Answer 27

The study of the interaction between matter and light.

Question 28

Strain

Answer 28

Distortion or deformation in a crystal.

Question 29

Stress

Answer 29

The force required to produce distortion in the crystal lattice.

Question 30

Surface Graining

Answer 30

Colorless lines or grooves on a diamond crystal’s surface.

Question 31

Tetrahedron

Answer 31

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

Question 32

Trace Elements

Answer 32

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

Question 33

Trigon

Answer 33

A triangular depression or protrusion that occurs on a diamond’s octahedral faces.

Question 34

Twinned Crystal

Answer 34

Crystal consisting of two or more parts formed in a symmetrical manner with shared crystal planes.

Question 35

Unit Cell

Answer 35

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

Question 36

Vacancy

Answer 36

A point defect created when an atom is missing from its original position in the crystal lattice.

Question 37

Volume Defect

Answer 37

Imperfection or deviation from the ideal arrangement of atoms caused by a three-dimensional aggregate of atoms or vacancies within the crystal lattice.

Question 38

Which type of bond is considered the strongest among atomic bonds?

Answer 38

Covalent bonds

Question 39

Why diamond is the hardest natural substance?

Answer 39

Because diamond’s atoms are more closely bonded than the atoms of any other material.

Question 40

What is the most common crystal habit of gem diamonds?

Answer 40

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

Question 41

What is true about defects in diamonds?

Answer 41

Defects in diamond are common and not always undesirable.

Question 42

What are the three common categories of defects found in diamonds?

Answer 42

Three categories of defects are common in diamonds: point, line, and volume.

Question 43

What factor is directly related to the increased strain in a diamond crystal?

Answer 43

The more dislocations that occur in a crystal, the more strain the crystal bears.

Question 44

What are examples of volume defects?

Answer 44

Mineral inclusions and voids are examples of volume defects.

Question 45

What structural feature in diamonds is mimicked by the shape of a negative crystal?

Answer 45

A negative crystal’s crystallographic shape always mimics the habit of the host.

Question 46

What forms the foundation of the diamond type classification system?

Answer 46

The foundation of the diamond type classification system is the presence or absence of nitrogen and boron atoms and the way they are arranged in the crystal lattice.

Question 47

What is a defining characteristic of Type I diamonds?

Answer 47

Type I diamonds have nitrogen atoms replacing carbon atoms in their crystal lattice.

Question 48

What is true about most Type I diamonds?

Answer 48

Most type I diamonds are a mix of more than one diamond type.

Question 49

What is a characteristic feature of Type IIa diamonds?

Answer 49

Type IIa diamonds have no easily measurable nitrogen or boron impurities in the crystal lattice.

Question 50

What type of atomic impurities are present in type IIb diamonds?

Answer 50

Type IIb diamonds contain boron atoms replacing carbon atoms within the crystal lattice, as well as a negligible amount of nitrogen impurities.

Question 51

Which method is most reliable for determining a diamond's type?

Answer 51

The most reliable and precise determination of diamond type is by spectroscopy.

Question 52

What is true about the crystal planes present in all diamonds?

Answer 52

All diamonds, regardless of their external appearance, contain cubic, octahedral, and dodecahedral crystal planes.

Question 53

Which plane in a diamond provides the most efficient sawing direction?

Answer 53

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

Question 54

What is true about polishing diamonds in relation to surface grain lines?

Answer 54

It is easier to polish against surface grain lines than along them.

Question 55

Which planes in a diamond are considered cleavage planes?

Answer 55

Diamond’s octahedral planes are cleavage planes.

Question 56

What does a trigon on a diamond signify?

Answer 56

A trigon indicates an octahedral plane in a diamond.

Question 57

Resorption in diamonds leads to a combination of which crystal forms?

Answer 57

A combination of octahedral and dodecahedral forms can be caused by resorption.

Question 58

What is the most common form of twinned diamond crystal?

Answer 58

The macle is the most common twinned diamond crystal.

Question 59

What is the single most important value factor for cuttable rough diamonds?

Answer 59

Shape is the single most important value factor for cuttable rough diamond. A well-shaped rough diamond allows for a more efficient cut, minimizing weight loss while maximizing the yield of the final polished gem.