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Colored Stone Essentials > 2 - Color and Phenomena > Flashcards

2 - Color and Phenomena Flashcards

1
Q

Adularescence

A

The cloudy bluish white light in a moonstone, caused by scattering of light.

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2
Q

Asterism

A

Crossing of chatoyant bands, creating a star in the dome of a cabochon.

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3
Q

Aventurescence

A

A glittery effect caused by light reflecting from small, flat inclusions within a gemstone.

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4
Q

Bodycolor

A

A gemstone’s basic color, determined by its selective absorption of light.

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5
Q

Chatoyancy

A

Bands of light in certain gems, caused by reflection of light from many parallel, needle-like inclusions or hollow tubes.

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6
Q

Color center

A

A small defect in the atomic structure of a material that can absorb light and give rise to a color

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7
Q

Color change

A

A distinct change in gem color under different types of lighting.

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8
Q

Color range

A

The selection of colors in which a gemstone occurs.

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9
Q

Color zoning

A

Areas of different color in a gem, caused by variations in growth conditions.

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10
Q

Dispersion

A

The separation of white light into spectral colors.

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11
Q

Extinction

A

Dark areas in a faceted transparent colored stone.

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12
Q

Fine color

A

The color or colors in a gemstone’s color range considered by the trade to be the most desirable.

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13
Q

Fluorescence

A

Emission of visible light by a material when it’s stimulated by UV radiation.

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14
Q

Hue

A

The first impression of an object’s basic color.

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15
Q

Iridescence

A

A rainbow effect created when light is broken up into spectral hues by thin layers.

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16
Q

Labradorescence

A

A broad flash of color in labradorite feldspar that disappears when the gem is moved.

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17
Q

Milk and honey

A

A two-toned effect seen when a chatoyant gem is positioned at right angles to a light source.

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18
Q

Orient

A

Iridescence seen in some natural and cultured pearls and mother-of-pearl

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19
Q

Play-of-color

A

The flashing rainbow colors in opal.

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20
Q

Pleochroism

A

When a gem shows different bodycolors from different directions.

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21
Q

Saturation

A

A color’s strength or intensity.

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22
Q

Selective absorption

A

Process by which a material absorbs some components of visible light and returns others.

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23
Q

Tone

A

Degree of darkness or lightness of a color.

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24
Q

Trade terms

A

Terms often used in the jewelry industry to describe particular gemstone colors or link gems with specific geographic locations.

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25
Q

What is a window and how does it arise?

A

An area of weak saturation in a transparent gemstone’s bodycolor that usually results from the way a gem was cut.

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26
Q

What is the top factor in what makes a gem desirable?

A

Color

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27
Q

Color is born from a reaction of these three things.

A

Light, an object, and an observer.

28
Q

What are the color components of white light called?

A

Spectral hues.

29
Q

When describing a color, would you use “medium dark vivid blue” or “cornflower blue”? Why?

A

“Cornflower blue” because everyday terms are more relatable to the consumer than technical terms.

30
Q

What determines whether a gem displays more than one color?

A

How it absorbs and returns light, its structure, and which combination of chemicals it contains.

31
Q

When is color zoning preferable?

A

When a gem has particularly striking distinct color zones.

32
Q

Parti-colored gems

A

When a gem with two or more distinct color zones. A subset is a gem with two zones, called bicolor gems.

33
Q

In what kind of light do green, blue, and violet gems look the best?

A

Fluorescent, due to the light’s greater presence of green and blue waves.

34
Q

In what kind of light do red, orange, and yellow gems look the best and why?

A

Incandescent, candlelight, a warm lamp, or the sun at sunset. This is because these lighting sources give off light waves mainly in red, orange, and yellow.

35
Q

How can a cutter minimize color zoning?

A

A cutter can position darker color zoning at the bottom of a gem, allowing the color to reflect throughout the stone when seen face-up.

36
Q

How can one observe a pleochroic effect in a gem?

A

In a traditionally unicolor stone (emerald), variation can most likely only be seen under magnification. For popular pleochroic stones (ex. Tanzanite), pleochroism can be seen by the naked eye.

37
Q

Is it possible to eliminate pleochroism?

A

No. It can be minimized but not eliminated.

38
Q

What are the usual qualities of fine color?

A

A “fine color” in a color range is usually medium to dark in tone and high in saturation.

39
Q

How can a window diminish a gem’s appearance?

A

It creates a see-through effect, possibly making a gem’s bodycolor uneven.

40
Q

How can a window enhance a gem’s appearance?

A

If a gem’s bodycolor is very dark, a window can lighten it and make the stone more appealing.

41
Q

In what kind of gems is extinction most common?

A

Those with darker body colors such as ruby, red garnet, and blue sapphire.

42
Q

How do windowing and extinction affect a gem’s value?

A

They usually lower color quality and thus value in a gem.

43
Q

What is the yardstick by which experts decide prices within a species or variety?

A

Color

44
Q

Are color ranges typically wide or narrow?

A

They can be either. Some gems can come in many hues, while some are limited to a small band of the spectrum

45
Q

Is a stone’s color compared to others of its variety, or similarly-colored gems overall?

A

The cost of a stone depends on its color compared with other stones of the same variety, not with other similarly-colored gems.

46
Q

Do colored stones display fire?

A

For the most part, no. There are some exceptions such as dementoid garnet and zircon.

47
Q

Fire

A

The dispersion of light within a gem.

48
Q

Is UV radiation visible?

A

No, but the effects of UV radiation - fluorescence - can enhance the color of a gem.

49
Q

In what situation would a gem’s hue outside the normal range be more valuable than a gem’s hue within the usual range?

A

If the first gem’s saturation is high and the tone is medium-dark, it can be worth more than the gem with the “ideal” hue.

50
Q

What external factors affect a gem’s price or value?

A

Consumer demand and heritage.

51
Q

Why should you avoid using technical terms with customers?

A

Technical terms can overwhelm the customer with facts and special terminology.

52
Q

How can word pictures help you present color?

A

Word pictures can be tailored to a specific customer’s intentions, desires, and emotions.

53
Q

When can you use trade terms to enhance a presentation?

A

You can use technical terms if the customer is very curious about a specific aspect of a gem, or when the technical term lines up with colloquial speech.

54
Q

How does a precise color vocabulary help in the industry?

A

Retailers and suppliers often speak of gems sight-unseen, so accuracy is a must. Appraisal also relies heavily on a precise written description.

55
Q

When is a description unacceptable or illegal to use?

A

Using a misnomer (ex. “Black diamond” for hematite).

56
Q

What is a phenomenal gem?

A

Any gem that displays striking optical effects.

57
Q

How do phenomenal gems get their special effects?

A

Crystal structure and chemical composition, as well as the presence of certain kinds of inclusions.

58
Q

How does opal’s play-of-color arise?

A

Opals are composed of tiny spheres. When the spheres line up, light waves bend around the spheres and break up into spectral hues. Color is dependent on the size of the spheres and the way the light interacts with them.

59
Q

What kind of adularescence is preferred in moonstone?

A

Blue adularescence is preferred over white. Blue bodycolor is preferred over white body colors.

60
Q

What are the two different types of cat’s eye?

A

Chrysoberyl and quartz.

61
Q

What is the value of cat’s-eye chrysoberyl over quartz?

A

Chrysoberyl is very rare and expensive, while the quartz is a cheaper alternative.

62
Q

What determines the number of rays in a star?

A

A gem’s crystal structure. Corundum and quartz stones usually have 6 rays. Other gems can display 4 or 6 rays.

63
Q

How are chatoyant and asterist gems usually cut?

A

Cabochons, with domes high enough to display the asterism or chatoyant bands.

64
Q

What is a familiar example of aventurescence?

A

Goldstone glass, a man made material used in low-end fashion jewelry.

65
Q

What gems are naturally occurring with aventurescence?

A

Aventurine quartz and feldspar. In these gems, light reflects from small, flat inclusions in the stone.

66
Q

What are the main types of phenomena seen in gemstones, and some examples?

A

Play-of-color: opal
Adularescence: moonstone
Color change: alexandrite
Chatoyancy: cat’s-eye chrysoberyl and quartz
Milk-and-honey: cat’s-eye chrysoberyl
Asterism: star ruby and star sapphire
Labradorescence: labradorite
Iridescence: fire agate, pearls
Orient: pearls, mother of pearls
Aventurescence: goldstone, aventurine quartz, sunstone feldspar

Colored Stone Essentials (5 decks)

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