key_terms_ass_5 Flashcards
Aggregate
A solid mass of individual randomly oriented crystals intergrown or held together by a natural binding agent.
Atom
The basic structural unit of all matter.
Cleavage
A smooth flat break in a crystal parallel to a cleavage plane.
Cleavage Plane
A planar surface along which a mineral tends to break due to atomic weakness.
Covalent Bond
A chemical bond formed by two atoms sharing electrons.
Crystal
Solid matter with atoms arranged in a regular repeating pattern.
Crystal Axes
A reference system used to describe the symmetry and shape of crystals.
Crystal Planes
Any set of parallel and evenly spaced planes distributed along certain crystal directions in which atoms are more closely packed.
Crystal Shape (form)
The geometric shape of a well-formed crystal.
Crystal Structure (lattice)
The regular repeating arrangement of atoms in a mineral.
Crystal Systems
Categories of crystals based on their symmetry and internal structure.
Crystalline
Composed of crystals or related to crystals.
Defect
An imperfection or deviation from the ideal crystal lattice.
Doubly Refractive (anisotropic)
Possessing different physical or optical properties in different crystal directions.
Glassie
A well-shaped transparent octahedral diamond crystal with sharp square edges.
Glide Plane
The plane or surface in which a dislocation travels through the crystal to cause an offset.
Graining (Grain Lines)
Visible shadow-like lines in a diamond caused by glide planes in the crystal structure.
Growth Marks
Visible features on the surface of a mineral crystal that reflect its internal growth and development.
Habit
The characteristic crystal shape or form of a mineral.
Line Defect (Dislocation)
Imperfection or deviation from the ideal arrangement of atoms in relation to a line in the crystal lattice.
Macle
A flat triangular twinned diamond crystal.
Octahedron
A crystal shape with eight equal triangular faces.
Point Defect
An imperfection or deviation from the ideal arrangement of atoms in relation to a single atom or point in the crystal lattice.
Resorption
The process in which the outer surface of a diamond is partially dissolved during transport.
Singly Refractive (Isotropic)
Possessing the same physical or optical properties in all crystal directions.
Specific Gravity (SG)
The ratio of the weight of a material to the weight of an equal volume of water.
Spectroscopy
The study of the interaction between matter and light.
Strain
Distortion or deformation in a crystal.
Stress
The force required to produce distortion in the crystal lattice.
Surface Graining
Colorless lines or grooves on a diamond crystal’s surface.
Tetrahedron
In diamond a group of five carbon atoms with one at the center.
Trace Elements
Atoms in a gem that aren’t part of its essential chemical composition.
Trigon
A triangular depression or protrusion that occurs on a diamond’s octahedral faces.
Twinned Crystal
Crystal consisting of two or more parts formed in a symmetrical manner with shared crystal planes.
Unit Cell
The smallest group of atoms with the characteristic chemical composition and the basic crystal structure of a mineral.
Vacancy
A point defect created when an atom is missing from its original position in the crystal lattice.
Volume Defect
Imperfection or deviation from the ideal arrangement of atoms caused by a three-dimensional aggregate of atoms or vacancies within the crystal lattice.
Which type of bond is considered the strongest among atomic bonds?
Covalent bonds
Why diamond is the hardest natural substance?
Because diamond’s atoms are more closely bonded than the atoms of any other material.
What is the most common crystal habit of gem diamonds?
The most common habit of a gem diamond is the octahedron, but perfectly shaped octahedral rough is rare.
What is true about defects in diamonds?
Defects in diamond are common and not always undesirable.
What are the three common categories of defects found in diamonds?
Three categories of defects are common in diamonds: point, line, and volume.
What factor is directly related to the increased strain in a diamond crystal?
The more dislocations that occur in a crystal, the more strain the crystal bears.
What are examples of volume defects?
Mineral inclusions and voids are examples of volume defects.
What structural feature in diamonds is mimicked by the shape of a negative crystal?
A negative crystal’s crystallographic shape always mimics the habit of the host.
What forms the foundation of the diamond type classification system?
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.
What is a defining characteristic of Type I diamonds?
Type I diamonds have nitrogen atoms replacing carbon atoms in their crystal lattice.
What is true about most Type I diamonds?
Most type I diamonds are a mix of more than one diamond type.
What is a characteristic feature of Type IIa diamonds?
Type IIa diamonds have no easily measurable nitrogen or boron impurities in the crystal lattice.
What type of atomic impurities are present in type IIb diamonds?
Type IIb diamonds contain boron atoms replacing carbon atoms within the crystal lattice, as well as a negligible amount
of nitrogen impurities.
Which method is most reliable for determining a diamond’s type?
The most reliable and precise determination of diamond type
is by spectroscopy.
What is true about the crystal planes present in all diamonds?
All diamonds, regardless of their external appearance, contain cubic, octahedral, and dodecahedral crystal planes.
Which plane in a diamond provides the most efficient sawing direction?
Cubic planes provide the most efficient sawing directions for dividing large, regularly shaped crystals.
What is true about polishing diamonds in relation to surface grain lines?
It is easier to polish against surface grain lines than along them.
Which planes in a diamond are considered cleavage planes?
Diamond’s octahedral planes are cleavage planes.
What does a trigon on a diamond signify?
A trigon indicates an octahedral plane in a diamond.
Resorption in diamonds leads to a combination of which crystal forms?
A combination of octahedral and dodecahedral forms can be caused by resorption.
What is the most common form of twinned diamond crystal?
The macle is the most common twinned diamond crystal.
What is the single most important value factor for cuttable rough diamonds?
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.
