Chapter 5 Diamond Crystal Flashcards
Where from word crystal comes?
From Greek krystallos, which means “clear ice”.
Are crystals organic or inorganic?
Both
What scientists have discovered regarding crystals?
That almost all solids are crystalline.
Give examples of the crystalline materials in daily life?
Teeth, bones, sugar, salt, snow, ice, sand, aspirin, steel and nylon.
What determines atom’s chemical nature - ability to combine with other atoms?
The number of electrons in an atom’s outer shell.
Which atom is chemically inert?
One with a full outer shell.
How many electrons are present in the outer shell of a carbon atom?
Four
How many spaces are available in the outer shell of a carbon atom for additional electrons?
Four
What is represented by the atomic number?
Atomic number represents the number of protons in the atom’s nucleus.
What type of geometric figure is a tetrahedron?
Tetrahedron is four-sided figure with triangular sides.
Name three forms crystal shapes of diamond crystal?
Cube, octahedron, dodecahedron
What is S.G. of gem quality diamond?
3.52 g/cm3
What is S.G. of industrial grade diamond?
From 3.52 g/cm3 to 3.43 g/cm3
How many directions of perfect cleavage diamond has?
4
Which mineral crystal has 4 cleavage planes like diamond?
Fluorite
What does the word ‘hedron’ mean?
Face
What is shape of diamond’s unit cell?
It’s cube shaped.
What is usual diamond habit?
Gem’s diamond habit is octahedron, form with eight triangular faces.
Does crystal structure affects weight?
Yes, it affects Density.
How much times more diamond weighs than graphite?
1.6
What is S.G. of graphite?
2.23
What is S.G. of diamond?
3.52
How many cleavage planes has mica?
1
How many cleavage planes has diopside?
2
How many cleavage planes has corundum?
None
What crystal structure have platinum & gold?
Cubic, like diamond.
Name 3 categories of deffects possible in diamond?
Point, line and volume.
What coexistence of different diamond defects can give?
A rise to diamond’s unique body-colors.
How is intrinsic point defect created in diamond?
When a carbon atom is missing from its original position, creating a vacancy.
How is extrinsic point defect occurs in diamond?
When foreign elements, or trace elements, replace a carbon atom in diamond’s crystal lattice.
When extrinsic defects occur in general?
Extrinsic defects occur when diamonds incorporate atoms of elements not part of their essential chemical composition.
What are atoms or elements that are not part of the chemical composition called?
Trace elements or impurity elements.
What trace elements can cause in diamond’s crystal lattice if they are not same size as carbon atoms?
They can cause distortions in the crystal lattice.
When dislocations occur in diamond?
Dislocations occur when stress is applied to the crystal lattice and produces distortion.
What dislocations provide?
Dislocations provide a mechanism by which permanent shape change, or deformation, occurs in a crystal lattice.
What means if diamond has a lot of strain?
That means in diamond there are plenty of dislocations.
What kind of stress can produce dislocations?
Change in environment such as change in pressure.
In which planes dislocation moves most easily?
Along the densest planes of atoms.
Why graining is useful for cutters?
Because if follows certain crystal orientations, so its in determining polishing directions.
Which kind of defects are taking place on larger scale?
Volume defects.
What type are vast majority of natural diamonds?
They are type Ia
In how many ways aggregated nitrogen atoms can be arranged?
In two ways. “A” aggregates and “B” aggregates.
What is A aggregates or A center?
When nitrogen atoms are aggregated in pairs within crystal lattice.
What is B aggregates or B center?
When nitrogen atoms are aggregated in groups of four next to a vacancy in the crystal lattice.
What type of diamond type are most type I diamonds?
They are mixed type of more than one diamond type.
What do scientists believe regarding diamond type during it’s formation?
Scientists believe that when diamond form, all nitrogen impurities occur as isolated nitrogen atoms - Type Ib.
What happens with isolated nitrogen impurities during diamond formation in mantle?
Isolated nitrogen impurities diffuse through the diamond crystal lattice and aggregate the longer they reside in the mantle.
What happens when two C centers combine in diamond?
They form A center.
What happens when two A centers combine in diamond’s crystal lattice?
They form B center.
What can be result of continuous progression of nitrogen impurity aggregation?
It can result in an almost “pure” type IaB diamond.
What can Ib diamonds exhibit?
They can have an extraordinary yellow color - called canary in the trade. (fancy vivid yellow)
What are known type IIA diamonds for?
For exceptional pureness.
What certain defects can cause in type II A diamonds?
Defects in IIA diamonds can cause brown, pink or gray body-color.
What you can tell about type IIA diamonds as conductors?
Type IIA diamonds are excellent conductors of heat.
Name three type IIB blue diamonds?
30.62 ct Blue Heart, 45.52 ct Hope, and 27.64 ct Heart of Eternity.
What you can tell about type IIB diamonds as conductors?
Type IIB diamonds are excellent conductors of electricity.
How many sets of internal crystal planes diamond has?
3 planes: cubic, octahedral and dodecahedral plane.
How are called crystal planes that reach the surface of the crystal?
Crystal face
How growth marks are useful for cutters?
Growth marks often give cutters critical clues about the orientation on the crystal planes within the diamond.
Are all growth mark same?
No, the type of growth mark and its orientation on the crystal surface vary on different crystal faces.
Which planes provide most efficient sawing directions for dividing large, regularly shaped crystals?
Cubic planes
Which direction of surface grain is better to polish?
Against surface grain lines.
What are tetragons and on which faces the can be found?
On cubic faces, tetragons are growth marks.
How tetragon is oriented on cubic face in diamond?
It’s oriented 45 0 angle to the cubic face.
Are gem-quality cube-shaped diamond crystals are common?
No they are extremely rare, and no cubic crystals have the perfectly flat crystal faces.
Do every diamond crystal has cubic planes parallel to its possible cubic crystal faces?
Yes
Do diamonds have only hard directions?
No diamond has soft and hard directions.
How many soft directions cubic plane has for polishing?
Two.
Which crystal planes provide the most efficient directions for sawing large, regularly shaped crystals into sections?
Cubic planes offer the most efficient directions for sawing large, regularly shaped crystals into sections.
What type of blemish is surface graining
It’s an growth mark.
Where surface graining can be seen?
It’s commonly seen on cubic, octahedral, & dodecahedral planes
What is one principle of cutting regarding grain lines?
To always polish against the grain lines instead along them.
In cubic plane how you should polish the crystal?
You should polish toward the edge of the square on a cubic plane.
What is found on surface of the cubic planes except surface graining?
Square depressions, called tetragons.
What could be helpful when finding tetragons on crystal face?
It can help determine the direction of the cubic crystal planes.
How octahedron shape looks like?
Looks like two four sided pyramids joined base to base.
What are internal octahedral planes?
These are the planes parallel to the possible octahedral faces.
Why octahedral planes are important in diamond?
They are important because planes parallel to to the possible octahedral faces are cleavage planes.
How cleavage is used by cutters?
Cutters use cleavage to divide distorted crystal into more workable shapes, and to remove major inclusions to improve clarity.
Are octahedral planes hard?
Yes they are very hard, resistant to scratching, and almost impossible to polish.
What is the only possible way to polish octahedral face?
The only possible way to polish an octahedral surface is to polish toward the edges. Cutter have to work at a slight angle to the octahedron’s surface.
How are surface grain lines distributed on octahedral faces?
They are parallel to three edges.
What kind of growth marks octahedral faces may also contain?
Trigons, triangular depressions of protrusions that occur on octahedral diamond’s faces.
How trigons are predominantly oriented to triangular face they are located in?
They are oriented in opposite direction, but there are some exceptions, when they are oriented same way.
Do the octahedral faces only exhibit trigons?
No, sometimes there are six sided pits, hexagons.
How usually hexagons look like in triangular face of octahedra?
Usually they have rounded outlines and are less common than trigon.
What you also may find on the surface of octahedral planes, besides trigons, hexagons?
You can find triangular plates.
How triangular plates are oriented to trigonal faces?
They are often of varying sizes, oriented in the same direction as the triangular faces.
How do triangular plates look alike?
They are usually layered on top of each other, producing a step-like appearance.
What is difference between trigons and triangular plates?
Triangular plates form during diamond crystal growth, while trigons arise after crystal growth is complete.
When twinning crystal occurs?
When the crystal’s growth is interrupted and it begins to grow again in different direction.
How is called surface along which diamond’s growth direction changes?
Twinning plane
Which is most common type of twinned diamond crystal?
Macle
What is seeing on the macle?
Surface graining and trigons.
Why macles are challenge for cutters?
- crystal structure reverse from one side to the other, so sawing and polishing directions are not continuous.
- are usually so shallow that they don’t yield round brilliants without significant weight loss
Which cuts is usually used for macles?
Macles are usually used for fancy shapes /triangles, hearts, and pears/
Can individual crystals always be seen with the unaided eye in an aggregate?
Sometimes crystals aren’t visible to the unaided eye. In those cases, detecting aggregate’s parts requires high magnification.
On which factor is based diamond rough’s value?
Diamond rough’s value is based on its potential as a faceted gem.
How rough sorting begins?
It begins with deciding whether a rough diamond is cuttable or non-cuttable.
What are usual characteristics of industrial quality diamonds?
They lacks transparency, and uniform shapes, some are cube shaped, colorless or colored.
What can be done with near-gem-quality diamond rough transparent portions?
It can be removed and processed by cleaving, sawing, or lasering.
What is done to judge rough diamond that has opaque coating?
The coating is polished away so buyer can judge its destiny as finished stone.
Is bort is used in jewelry?
Nowadays its being adopted by modern designers who find it interesting in colors and shape.
Enlist types of rough shapes in scale from more valuable to less valuable?
Sawable, Makeable, Splittable, Macle, Flat
What you can cut from sawable?
Usually large round billiants and princess cuts.
What you can cut from makeable?
Usually large round brilliants
What you can cut from splittable?
Round brilliants or fancy cuts
What you can cut from macle?
Fancy cuts usually small.
What you can cut from flats?
Baguettes or similar small stones.
Which property is affected by shape of rough regarding the cut?
Shape of rough affects how much weight cutter can retain in the finished gem.
Definition of makeable?
Makeable is diamond rough that can be polished without sawing, cleaving, or splitting. Final shape is a single stone that’s often similar to the shape of the rough.
How is called makeable if it’s shape is elongated?
It can be referred as irregular.
Definition of sawable?
It’s a diamond rough that will yield more weight if it’s divided to produce 2 stones.
What is usual shape of sawable?
Octahedron or a dodecahedron.
Definition of splittable or cleavage rough diamond?
It’s diamond rough that can be divided into small, but valuable, segments by lasering or cleaving.
Definition of flat rough?
A flat is a shallow crystal that’s very limited in its potential shape.
Definition of cleavage/splittable rough?
Cleavage applies to a piece of diamond rough that broke cleanly along a cleavage plane.
Fot what kind of diamonds rough DTC uses term “Cleavage”?
DTC uses term cleavage for broken, irregularly shaped pieces of rough that weigh over 1.80 ct.
What you can tell about cleavage rough diamonds?
Many of the world’s largest and most famous rough diamonds were cleavages.
What is must be considered when in case well-shaped rough diamonds?
Their potential of marketability. For example even if a piece rough can be large round brilliant, it might be easier to sell smaller gems.
What cutters must consider when deciding the shape of diamond?
Marketability and weight retention.
