Chapter 6 Flashcards
For how much Blue Moon diamond has being sold on auction?
For $48,5 million at Sotheby’s in 2015.
Which diamonds are called colored?
Colored diamonds are yellow and brown diamonds beyond D-Z range, and diamonds that exhibit any other color face-up.
What represents blue color?
Trust and royalty.
What red color conveys?
Excitement and demands attention.
Do everybody perceive color same way?
Color perception vary from person to person.
What is an color of object?
Object’s color is the result of interactions between light and the object as well the viewer’s interpretation.
What are main factors that influence color perception?
Light source, object, and observer.
When object can be seen?
If it returns light to observer’s eye.
What is light build of?
Light is a combination of electric and magnetic (electromagnetic) energies, and it travels in waves.
How much is one nanometer in millimeter?
One nm is one millionth of a millimeter.
What is electromagnetic spectrum?
It’s the range of wavelengths of radiant energy extending from high to low energy.
How much of electromagnetic spectrum can be detected by human eye?
Human eye can detect only visible light, which small portion of spectrum. Visible spectrum 400nm (violet) to about 700 nm (red wavelengths).
Which part of electromagnetic spectrum is invisible for human eye?
Not visible for human are: gamma rays, X-rays, Ultra Violet, Infrared, Radio Waves.
What is white light?
White light is the combination of colors in the visible spectrum: red, orange, yellow, green, blue and violet.
What can split beam of white light into spectral colors?
Prism
What happens when visible light meets a transparent faceted gem material?
Some light reflects off the stone’s surface, rest enters the stone, where the gem’s crystal structure absorbs some of the color components of the light.
What happens with component not absorbed by the gem?
It returns to observer eye - transmission - and present as the gem’s color.
What happens when little or no color is absorbed by the gem?
All spectral colors return to observer’s eye and the gem appears colorless.
What happens when all colors are absorbed by the gem?
The gem appears black.
What causes diamond’s color primarily?
Color is caused primarily by imperfections or defects in crystal lattice.
Do all the defects cause color in diamonds?
No.
How do you call defects that cause color in diamonds?
Color centers.
What do color centers-defects influence in diamond?
Color centers influence selective absorption of white light.
Are some diamonds can be separated from simulants or identified as treated?
Yes
What kind of material is diamond?
Crystalline
How many electrons surround carbon nucleus?
Six
What plays specially important role in selective absorption?
Electrons, because visible light interacts primarily with them.
What is the most cause of the gem colors caused by selective absorption?
Movement of electrons
When electron is stable?
Electron is stable at its lowest energy, it’s called ground state.
What happens when electron absorbs a specific wavelength of visible light?
Electron rise temporarily to higher level called and excited state.
How electron releases energy gained from light?
By returning to its ground state
How is called movement of electron between ground and excited state?
Transition.
How is called lower-energy band for electrons?
Valence band.
How is called higher-energy band for electrons?
Conduction band.
How is called constant energy difference between valence and conduction band?
Band gap.
Is width of band gap is constant for all electrons?
No width of gap varies by material.
What band gap width determines?
It determines how much energy an electron requires to move across the gap.
In which groups are solid materials divided based on their band structure?
Insulator, semiconductor, and conductor.
How in copper valence and conduction bands are positioned?
They overlap, so electrons move easily between them.
How valence and conduction bands are positioned in insulators?
Band gap is so large that energy provided by visible light is not enough to make electrons cross the gap.
What would be defect-free diamond in band theory?
An insulator.
When diamond could be perfectly colorless?
Diamond that lack structural defects (color centers) so it could not absorb any visible light.
What role play structural-defects in diamond in band theory?
Defects work as newly added steps in the band gap, so electrons can make transitions using them from ground to transition state.
What is other name for band theory?
Electronic band structure.
Explain how defects help electron to cross band gap?
Electron instead of crossing whole gap makes transitions between the conduction or valence band and these defect steps, or even between these steps. This way distance electrons need to travel is much shorter.
What precent of total rough diamond production is fancy color?
Around 2%
What is cause of color in diamonds in most cases?
Most colors in diamonds are caused by defects or imperfections (color centers) in the atomic lattice.
Is one type defect in diamond is cause of one type of color?
No, same defect can cause different colors based on concentration and presence of other defects.
Can color caused by defects be altered?
Yes, it can be altered with time in earth or by exposure to heat or radiation in the lab.
Which colored diamonds ar some of the most commonly encountered natural-color diamonds?
Yellow diamonds
Which defect is most common cause of yellow in type Ia diamonds?
The most common is the N3 color center, which consists of 3 N atoms adjacent to vacancy.
With which defect is usually associated N3 color center?
With another nitrogen-related defect N2 which also contributes yellow color.
How are often called natural yellow type Ia diamonds colored by N3 defect?
Cape
Which diamond is one of the most famous cape diamonds?
The 101,29 ct Allnatt diamond probably from De Beers mine in South Africa.
Who is Allnatt named after?
It is named after Major Alfred Ernest Allnatt, a british soldier, sportsman, art patron and philanthropist who purchased it in 1950’s.
What is, less common than N3 and N2 (defects), cause of yellow color in diamond?
Cause of color is isolated nitrogen atoms (C centers).
What type of diamonds are these who have majority nitrogen impurities as C centers?
Type Ib
How are called diamonds that are having highly saturated yellow or orange-yellow color?
Such diamonds are often described as “canary” diamonds in the trade.
Which defect is not well understood and produces staurated orangy yellow to yellowish orange coloration?
The naturally occuring defect 480 nm absorption band.
Which absorption band is associated with most common cause of pink color in diamonds?
The 550 nm absorption band, its associated with the deformation.
Which type diamonds usually contain smaller concentrations of nitrogen impurities, but their colors are highly saturated?
Type Ib.
Which combination of defect can also create orange-brown or brownish orange body color?
Combination of H3 centers and absorption band at 550 nm associated with deformation.
Which combination of defects can create extremely rare mix of yellow, pink or red colorS?
H3 defect 503,2 nm + 550 nm band
Give examples of famous orange diamonds?
The Pumpkin diamond 5.54 ct, discovered in South Africa in the mid-1990’s, the Orange a 14.82 ct pear shaped vivid orange,
For how much and when the Orange diamond has being sold at Christies?
In November 2013 it’s being sold for $35 million.
By whom Pumpkin diamond has being bought?
By Harry Winston Inc. at auction the day before Halloween in 1998.
In which colors one can find green diamonds?
Yellow-green, pure green, green dominant mixed with blue, brown or gray.
Where from most production of fine natural green diamonds is from?
From South America and Africa.
Which kind of green diamonds are most sought after?
Green stones with saturated colors.
What is most common cause of natural green color in diamonds?
It’s exposure to radioactive minerals and fluids in the earth’s crust over time.
What irradiation provides to displace carbon atoms from their normal positions in diamond lattice?
Energy
How are called vacancies in diamond’s crystal lattice caused by irradiation?
GR1- General Radiation 1
Why result of vacancies and or GR1 is green body color in diamond?
Vacancies known as General Radiation 1 defects, absorb red parts of visible light.
What color is produced by irradiation of light yellow diamond?
Usually irradiation produces a greener color.
What color is produced by irradiation of colorless diamond?
Irradiation produces a bluer color.
What is interstitial position?
Position that is taken by displaced atom, that it would not normally occupy.
Tlumacz interstitial atom?
Atom międzywęzłowy
What naturally irradiated diamonds usually have?
Naturally irradiated diamonds usually contain areas of green or brown radiation damage on their surfaces or penetrating into the stones. (patches of color or spots)
How radiation stain on diamond can be caused?
By direct contact with radioactive minerals, often in kimberlite host rock or interaction of radioactive fluids with diamond.
What happens when radioactive fluids interact with diamond?
Interaction with radioactive fluids , usually in alluvial environments, leave a coating (radiation skin) or penetrated fractures.
What happens when irradiation alternates only shallow layer of diamond?
A shallow green surface layer is typically removed during the cutting process.
In which temperature GR1 vacancies become mobile?
Above 600 C.
What happens to GR1 defected diamond when temperature of environment is above 600C?
GR1 becomes mobile, and new defects are created in diamond lattice, stone of color can change.
What jewelers have to consider when repairing jewelry with green diamonds?
They must take great care during repair to avoid heating the stone, which could result in removing the color due to destroying GR 1 defect. Same case can be with heat generated from friction of a polishing wheel.
Which defect is the second most common cause of green color in diamond?
H3 defect, primarily cause yellow body-color, but diamonds with abundant H3 defects and low concentrations of paired nitrogen impurities often emit enough green light under daylight equivalent to produce a combined yellow-green appearance.
Enlist four main causes of green color in diamonds?
GR1, H3, hydrogen related, and nickel related.
When Hydrogen-related defects can produce a green color component in hydrogen-rich diamonds?
When they are combined with nitrogen defects in the blue end of spectrum.
What color component is often present in green diamonds colored by hydrogen related defect?
These diamonds commonly have brown or gray color components.
Why green diamonds colored by nickel related defects are less common?
Because large size of the nickel atom that must be accommodated in the lattice.
Which defects occur concurrently with nickel-related defects in diamond?
With nitrogen impurities or other defects.
What color is typically exhibited by a nickel-related diamond with nitrogen-related absorption?
Typically nitrogen-related absorption is stronger than nickel-related absorption, so it produces yellow-green color.
With which impurities are H3, hydrogen, and nickel defects associated?
With nitrogen impurities.
What type of diamonds are usually green due to H3, hydrogen, and nickel defects?
Ia
Which type of diamond can be subjected to irradiation to develop GR1 defects and produce green or blue color?
Any type of diamond.
What you can observe in green diamonds colored by different defects?
Different defects display various color ranges.
Who bought Dresden Green?
Augustus the Strong in 1726
What is the weight of Dresden Green?
41 cts
What is chameleon diamond?
These diamonds when they are heated or left in the dark for extended period of time they temporarily lose their green color and change to yellow or orangy hues.
Which type usually are chameleon diamonds?
Usually these are type IaA diamonds that exhibit an unknown absorption feature at 480 nm and an absorption band related to hydrogen or nickel impurities.
Does the nature of color change of chameleon diamonds is known?
No
Which hint of color is visible in blue diamonds?
Blue diamonds generally have a slight hint of gray, so their color is never highly saturated as blue sapphires.
What are three main causes in blue color range?
Boron (type IIb diamonds), hydrogen-related defects, and GR1 defects.
Name largest violet diamond from Rio Tinto’s Argyle diamond mine?
2,83-ct. oval Argyle Violet Fancy Deep grayish bluish violet.
Which defect can produce green, blue, violet and gray color in diamond?
Hydrogen related defect
Where from color of hydrogen-defect results from?
From two broad absorption bands creating two transmitted colors in the blue and red regions of the visible spectrum.
What determines whether the stone with hydrogen defect appears more blue or violet?
Relative strength of red and blue colors caused by absorption lines.
What can also cause gray color in diamonds?
The presence of micro inclusions.
Which colors of diamonds are rarest of all natural diamonds?
Pure red and pure purple.
What is main cause of pink-to-red, purple and brown colors in diamond?
Main cause is absorption band centered approximately 550 nm in the visible spectrum.
What 550 nm defect makes?
550 nm defect allows the yellow/green portion of the visible light spectrum to be absorbed and red to be transmitted.
With what can be correlated 550 nm defect?
This defect is correlated with deformation, but its nature has not been identified yet.
What can alter the color in diamonds type Ia with 550 nm absp. band?
N3 and H3 defects in type Ia results in differences in color.
Where color is concentrated in many pink, red, purple and brown diamonds?
It is often concentrated within parallel narrow bands called colored lamellae.
How are called closely spaced grain lines in colored diamond?
Colored lamellae.
What causes the formation of colored lamellae in colored diamonds?
Closely spaced grain lines resulting from deformation.
Are there red-to-pink diamonds with uniform color distribution?
Yes
What is the reason of pale pink color in type II a diamond?
NV defect (single nitrogen associated with vacancy). Caution: natural pink diamonds colored by NV defect are extremely rare.
Which defect is most exclusively the cause of pink color in treated and lab-grown diamonds?
NV defect.
Which color is most common of colored diamonds?
Yellow & Brown
Which defect is present in vast majority of brown diamonds?
Vast majority of diamonds have colour due to vacancy clusters generated by deformation.
What cause vacancy clusters across the visible spectrum?
Vacancy clusters cause a gradually decreasing absorption across visible spectrum toward the red end.
Name 3 famous red diamonds?
0.95 ct Hancock red, 5.11 ct Moussaieff Red, 2.11 ct Argyle Everglow
Where Moussaieff has being recovered?
In Brazil, by farmer from an alluvial deposit.
What was the rough weight of Moussaieff red diamond?
13.90 ct
Who manufactured Moussaieff red diamond and where?
William Goldberg Diamond Corp. in New York into modified triangular brilliant.
Name most famous black diamond
The Black Orlov
Which type of diamond is Moussaieff red diamond?
Type Ia
When the beauty of black diamonds began to intrigue jewelry designers?
In late 1990’s
What is the weight of Black Orlov?
67.50 ct
What is the usual reason of black and white color of diamonds ?
Volume defects such as internal inclusions that reduce the transparency of the diamond.
What is the usual reason of color in natural black diamonds?
Usually black diamonds are colored by dark inclusions of graphite, sulfide, magnetite, hematite, or other iron-bearing minerals.
Where is important source of black, gray, and brown diamonds?
In Marange alluvial deposit in Zimbabwe.
Which terms are often used to describe the appearance of white diamonds?
Hazy, milky, or cloudy.
What are two distinct causes of opalescence, hazy, milky or cloudy appearance of white diamonds?
Nano inclusions and structural imperfections.
What is fluorescence?
Fluorescence is a form of luminescence that occurs during the time a gemstone is exposed to high-energy radiation.
What is phosphorescence?
Continued emission of visible light after UV or X-ray stimulation stops.
Why there are different colors of fluorescence in diamonds?
Different defects are located at different positions in the band gap. When electrons return from various positions, they release different levels of energy and cause different fluorescence colors.
Which color of fluorescence give NV defect?
Red, yellow, orange.
Which color of fluorescence give H3 defects?
Green
Which color of fluorescence give N3 defects?
Blue, more defect more intense color.
How many precent of colorless natural diamonds emit fluorescence to UV radiation?
35%
Which color of fluorescence give 480 band defects?
Yellow
Does the nature of the excitation source can also affect the observed fluorescence?
Yes
What are most commonly used light sources for luminescence?
Short UV (254nm) and long UV (365nm)
When luminescence is useful in diamond testing?
It is useful for screening small diamonds because it allows for quick spotting of stones that require further testing.
