ASS #5 - Diamond Crystal Structure and Atomic Theory

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Questions and Answers

What defines the chemical nature of an atom?

The total number of neutrons in the nucleus

The total number of all subatomic particles

The number of protons in the nucleus

The number of electrons in its outer shell (correct)

Which of the following statements about the diamond unit cell is true?

The core of diamond's unit cell is formed from multiple layers of tetrahedrons

The unit cell sets the standard for repeated patterns in the crystal (correct)

A unit cell contains only one type of atom

A unit cell can exist independently of other cells

What shape does diamond most commonly exhibit in its crystal habit?

Hexagonal prism

Octahedron (correct)

Dodecahedron

Cube

What type of bond is primarily responsible for the strength of diamond?

Covalent bond Signup and view all the answers

What is the atomic arrangement in diamond as formed by its carbon atoms?

Tetrahedrons connected by shared electrons Signup and view all the answers

What characteristic of diamond allows it to have a unique crystal structure?

Extreme pressure during formation Signup and view all the answers

Which of these describes the term 'crystal habit'?

The external shape of the crystal formed by unit cells Signup and view all the answers

Which statement is incorrect regarding the formation of crystals?

Crystals always have an organic origin Signup and view all the answers

What is the most common habit of gem-quality diamonds?

Octahedron Signup and view all the answers

What is a primary characteristic of twinned crystals?

They form when growth is interrupted and resumes in a different direction. Signup and view all the answers

Which type of diamond aggregate is commonly used as an industrial abrasive?

Carbonado Signup and view all the answers

What distinguishes gem-quality diamond rough from industrial-quality diamond rough?

Gem-quality diamonds have a more uniform shape. Signup and view all the answers

What is the process called when the outer surface of a diamond is partially dissolved?

Resorption Signup and view all the answers

What is the common appearance of a macle diamond?

Flattened triangle Signup and view all the answers

How can strain in rough diamonds be identified?

Through the use of magnification and cross-polarized filters Signup and view all the answers

What happens to diamonds during the resorption process?

Their outer surface becomes smooth and rounded. Signup and view all the answers

What characterizes diamond octahedrons?

They are shaped with sharp, square edges. Signup and view all the answers

How does the crystal structure of diamond affect its density compared to graphite?

Diamond has a higher density because of a closer arrangement of carbon atoms. Signup and view all the answers

What defines cleavage planes in crystals?

They are surfaces where a mineral tends to break due to atomic weaknesses. Signup and view all the answers

What is a characteristic of cubic crystals regarding light behavior?

They are described as singly refractive or isotropic. Signup and view all the answers

What are point, line, and volume categorized as in diamond structures?

Categories of lattice defects. Signup and view all the answers

What typically causes defects in diamond crystals?

Environmental changes and impurities. Signup and view all the answers

What feature is NOT a characteristic of gemologists classifying crystals?

The color of the crystal. Signup and view all the answers

Which crystal shape is NOT part of the cubic system?

Hexagonal prism Signup and view all the answers

What is specific gravity (SG) in relation to diamonds?

The relationship between weight and volume of a substance. Signup and view all the answers

What term describes the smooth, flat breaks in crystals that occur along planes of weakness?

Cleavage planes Signup and view all the answers

Which characteristic describes how light behaves in cubic crystals?

Light behaves the same regardless of direction. Signup and view all the answers

Which type of defect in diamonds involves a deviation from the ideal structure?

Lattice defect Signup and view all the answers

What does the term 'octahedron' refer to in the context of diamond crystal shapes?

A shape with eight triangular faces. Signup and view all the answers

How much heavier is a diamond compared to graphite of the same size?

Approximately 1.6 times as much. Signup and view all the answers

What classification do gemologists use for categorizing crystals based on their geometric properties?

Crystal systems Signup and view all the answers

What is a common characteristic of simulants compared to diamonds?

Simulants tend to have higher specific gravity than diamonds. Signup and view all the answers

What is the structure formed by carbon atoms in diamond?

Tetrahedral arrangement Signup and view all the answers

Which type of bond in diamond contributes to its exceptional hardness?

Covalent bonds Signup and view all the answers

What is the unit cell's role in crystal structure?

To serve as a template for repeated patterns Signup and view all the answers

How do crystal shapes provide insight into atomic structures?

By reflecting the arrangement of atoms within the crystal Signup and view all the answers

What geometric form does diamond predominantly exhibit in its crystal habit?

Octahedron Signup and view all the answers

What type of crystals can diamonds form when subjected to high pressure?

Cubic crystals Signup and view all the answers

What defines the characteristic crystal habit of diamonds?

The arrangement of the unit cells Signup and view all the answers

Which feature is typical of the carbon atom's arrangement in diamond?

Grouped tetrahedrons Signup and view all the answers

What is typically indicated by the presence of strain in rough diamonds?

They might be more vulnerable during cutting. Signup and view all the answers

What defines a macle diamond?

It appears as a flattened triangle with surface graining. Signup and view all the answers

What is a common challenge faced by cutters when dealing with twinned diamond crystals?

The sawing and polishing directions are inconsistent. Signup and view all the answers

Why are dodecahedron crystals well-suited for being fashioned into round brilliants?

Their structure allows for optimal light reflection. Signup and view all the answers

How can the presence of aggregates in diamonds be described?

They are solid masses of randomly oriented crystals. Signup and view all the answers

What is a distinguishing factor for identifying gem-quality diamond rough?

More uniform shape and higher transparency Signup and view all the answers

Which of the following statements best describes the characteristics of industrial-quality diamond rough?

It typically lacks transparency and uniform shape. Signup and view all the answers

What is the primary cause of the formation of resorbed diamond crystals?

The outer surface is partially dissolved during transport. Signup and view all the answers

What is another name for the cubic system?

octahedron and dodecahedron Signup and view all the answers

Study Notes

Diamond Crystal Structure

Diamond crystals were described as symmetrical mineral specimens in the 17th century.
Crystals can be organic or inorganic and are found in plants, animals, as well as rocks and in labs.
All solids are crystalline

Atomic Structure

Atoms contain subatomic particles: protons, neutrons, and electrons.
Protons and neutrons form the nucleus at the atom's center. Electrons orbit the nucleus.
The number of electrons in an atom's outermost shell determines its chemical properties.
Carbon atoms in diamond share electrons with four neighboring atoms forming covalent bonds.
Covalent bonds are the strongest type of bond.
Carbon atoms are arranged in groups of five, with one central atom and four surrounding ones
This pattern is known as a tetrahedron.

Diamond Unit Cell

A unit cell is the smallest repeating unit in a crystal.
Diamond's unit cell is made of four tetrahedrons connected by strong covalent bonds.
Diamond's atoms are tightly packed compared to other materials.
This tight packing results in a high density compared to graphite.

Crystal Shape

Diamond's most common crystal shape is the octahedron (eight equal triangular faces).
Some diamonds display a perfect, octahedral shape.
The internal arrangement of atoms gives rise to different crystal shapes.
Crystal structure influences a crystal's density and specific gravity (SG).
Diamond has a higher SG than most other gemstones.

Cleavage Planes

Cleavage planes are directions in a crystal where it tends to break easily, due to atomic weakness.
Diamonds have cleavage planes that are parallel to certain shapes.
Cleavage planes exhibit smooth, flat breaking along the crystal.
Cleavage can be a useful property for recognizing and classifying crystals.

Crystal Defects

Imperfections in the crystal structure are called defects.
Point defects: Missing or misplaced atoms.
Line defects (dislocations): Imperfections in alignment.
Volume defects: Inclusion of foreign materials or voids.
Nitrogen and boron are common trace elements causing defects in diamond.

Diamond Classification

Diamond types are classified based on the presence and arrangement of impurities like nitrogen and boron.
Type 1 diamonds contain nitrogen impurities.
Type 2 diamonds have either no or minimal impurities, including Type IIa and IIb.
Type IIa diamonds are exceptionally pure and usually colorless.
Type IIb diamonds are rare, containing boron impurities.

Diamond Cut Potential

Diamond planes are internally arranged in a cubic, octahedral and dodecahedral pattern.
Cutters consider the marketability and weight retention when determining the rough diamond cutting shape.
A makeable rough diamond can be polished without cutting , sawing or splitting.
A sawable diamond can be cut into more valuable smaller pieces
A splittable diamond can be lasered or cleaved to form smaller, valuable segments
A flat diamond shape, restricts potential size and value

Diamond Value

Diamond shape is a major factor affecting value in the finished gem.
Cutters must consider weight retention and marketability when deciding on a cut's proportions.
Various factors (e.g., shape, clarity, and color) affect a diamond's value.

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Description

Explore the fascinating world of diamond crystals and atomic structure. This quiz covers the properties of diamond, the basics of atomic theory, and the unique tetrahedral arrangement of carbon atoms. Test your knowledge on the formation of covalent bonds and the significance of unit cells in crystals.