3 - Clarity, Cut, and Carat Weight Flashcards
Clarity
A gemstone’s relative freedom from inclusions and blemishes.
Blemish
Characteristic or irregularity confined to the surface of a polished gemstone.
Inclusion
A characteristic enclosed within a gemstone, or reaching its surface from the interior.
Clarity Characteristic
Internal or external feature of a gemstone that helps determine quality.
What three value factors is clarity related to?
Appearance, durability, and rarity.
What determines the influence of inclusions on value?
Size, number, position, color/relief, nature
Break
Classified as inclusion. The three kinds ore cleave, parting, and fracture.
Cleavage
A smooth, flat break in a gemstone parallel to planes of atomic weakness. Results from vulnerability in a gem’s structure.
Which kind of break is the most threatening?
Cleavage.
In which gemstones is it common to see cleavage?
Topaz, tanzanite, moonstone, and diamonds.
Parting
A flat break in a gemstone parallel to a twinning plane.
Twinning Plane
Location of a change in direction in a gem’s crystal structure, established during growth.
Fracture
Any break in a gem other than cleavage or parting. Often have scalloped shape.
When do fractures occur?
During growth or the mining process.
How can a fracture’s appearance be mitigated?
Fill with resin or epoxy.
Fluid inclusions
Small pocket in a gem that’s filled with fluids and, sometimes, glass bubbles and tiny crystals. Can affect a gem’s appearance, value, and ability to endure jewelry processes.
Included crystal
A mineral crystal trapped within a gem as it grows.
Eye-clean
When a gem’ inclusions are visible only under magnification.
Examples of typically eye-clean species
Aquamarine, citrine, kunzite, tanzanite, topaz
How is the value of a typically eye-clean gem affected by inclusions?
In the case of eye-clean gems, a stone will be more affected by the presence of inclusions than on typically visibly-included stones.
Helpful inclusion
An inclusion that contributes to a pleasing optical effect.
Silk
A group of fine, needle-like inclusions; helpful in cat’s-eye, star corundums, and fine blue sapphires.
What are two types of helpful inclusions?
Silk and horsetails
Horsetails
Wisps of long, gold, fiber-like inclusions that radiate from a central point. Present in demantoid garnets.
What would would you use to describe inclusions to a consumer?
“Characteristics” or “inclusions”. “Feathers” are allowed but should be explained.
When must you inform a customer of an inclusion?
If the inclusion affects durability.
Cut
the human contribution to a stone’s appearance. Helps with the display of color, influences clarity, and affects carat weight.
Shape
the face-up outline of a gem
Style
the arrangement of a stone’s facets.
Proportions
The angles and relative measurements of a polished gem, and the relationships between them.
Finish
The quality of the polish and precision of a cut of a fashioned stone.
Describe the parts of a round stone.
Crown, girdle, pavilion.
Describe the parts of a marquise stone.
Point, wing, belly.
Describe the parts of a heart-shaped stone.
Cleft, lobe, belly, wing, point.
Describe the parts of a pear-shaped stone.
Head, shoulder, belly, wing, point.
What are the most common cuts?
Brilliant, mixed, or step (emerald)
Brilliant cut
Triangular or kite-shaped facets that radiate toward the center toward the girdle.
Step cut
Mainly square or rectangular facets arranged in concentric rows.
Mixed cut
Combines brilliant- and step-cut facets.
Fancy shape
Any shape other than round.
Facet
A flat, polished surface on a finished gem.
Name five fancy shapes.
Baguette
Square
Rectangular & square antique
Rectangular & square step cut
Heart
Pear
Triangular step-cut
Triangular brilliant cut
Oval
Marquiese
Describe the extra component of a rectangular antique shape?
Arch.
Describe the extra components of a rectangular step cut?
Corner, side.
What natural process helps determine type of cut?
Some gems develop typical shapes and sizes that lend themselves well to certain cuts.
How are rubies and sapphires weighing more than 1ct typically cut?
Rubies and sapphires that weigh more than a carat are traditionally mixed ovals or antique cushions in order to retain max weight from the rough.
How are emeralds typically cut?
Lend themselves to rectangular cuts.
Cabochon
A smoothly rounded polished gem with a domed top and flat or curved base.
What are the three types of cabochon shapes?
Simple cab, double cab, buff top.
Simple cab
A cabochon with a rounded top and flat bottom.
Double cab
A cabochon with a rounded top and bottom.
Buff top
A cabochon with a rounded top and faceted pavilion.
When are cabochons used?
For phenomenal gems, and translucent or opaque stone.
Intaglio
A design engraved into the surface of a gemstone (usually on a flat, tablet-like stone).
In what kind of jewelry are intaglios normally found?
Men’s jewelry with opaque gems.
Cameo
A gem carving in which the design (often a woman’s profile), projects slightly from a flat or curved surface.
What materials are used for cameos?
Materials with color bands or other variations for contrast.
Three-dimensional
Standalone carvings akin to mini statues.
What kind of material is popular for 3D shapes?
Jade and serpentine.
How do extreme proportion variations affect a gem’s beauty and durability?
Proportion variations can reduce a gem’s beauty and durability.
Name three components of a proportional gem.
1) Profile should be symmetrical
2) Girdle should form a clean edge.
3) 1/4-1/3 of the stone should fall above the girdle
Saving (retaining) weight
Compromising beauty to remove less rough thus creating a heavier gem.
How does a thinner or deeper cut affect a gem?
A thinner stone can lighten the color, while a deeper cut can darken.
How does a wider table affect the apparent optics on a stone?
A wider table can make a stone look bigger.
Why are stones with extreme variations difficult to use in jewelry?
They are difficult to mount, unless given a complimentary setting.
Scintillation
Flashed of light displayed by a polished gemstone when the gem, observer, or light source moves.
What are the three components of an evaluation of finish?
1) Facet shape and placement
2) Number of facets and symmetry
3) Scintillation
What two factors are taken into account when evaluating polish quality?
1) “Shine”
2) Presence or absence of blemishes.
Why do manufacturers have different standards for cutting colored stones vs diamonds?
A colored gemstone requires a cut to best display its best attribute - color. Diamond cutters focus on bringing out brilliance and fire.
Do colored stones yield more or less weight with fancy shapes?
More weight (usually.)
Calibrated sizes
Gemstone sizes cut to fit standard mountings.
What is the relative value of gemstones cut to calibrated sizes?
Calibrated gemstones are often mass produced and thus less valuable.
Designer cuts
Artistic gem cuts that aren’t limited to specific proportions or shapes.
Why do designer cuts have special proportions?
Usually because of a rough stone’s optical characteristics.
Fantasy cut
A free-form cut that can feature alternating curved and flat surfaces. Often one-of-a-kind.
What is a mass-produced fantasy-cut?
Checkerboard.
How are smaller vs larger stones cut?
Smaller stones are usually cut in calibrated sizes, whereas the larger are usually cut symmetrically.
Metric carat
International unit for gem weight. 1ct = 0.2g
Point
1 pt = 0.01ct
How do jewelry professionals discuss carat weight?
In ranges, using fractions as reference points.
What is the least important value factor among color, weight, and cut?
Cut.
What units would be used with a customer?
Carats and their relative fraction (no points)
When is it okay to combine the gem weight for all stones in a piece?
When the result is used with the term “total gem weight”, in a way that the customer understands.
Total gem weight
The combined weight of all the stones in a piece of jewelry containing a variety of gems.
Per-carat price
The price of the gem divided by its carat weight.
How would a wholesale dealer quote value of a stone?
Either in per-carat price or stone price.
How does price vary with weight?
Price usually goes up, but the degree to which it does is dependent on the gem.
How does knowing per-carat price allow you to distinguish between different gems?
Between the same variety, it allows one to obviously identify the size and thus rarity. Between other gems, it can show how valuable one is compared to another.
When might a 4ct stone be more valuable than a 10ct stone?
If the 4ct stone naturally occurs in smaller sizes, this would make it worth more than a 10ct gem that frequently occurs in that 10ct range.
What is the “Fifth Value Factor”
After the 4Cs, customer preference is considered the fifth value factor.
Density
weight relative to size; how close together the atoms of a gem are.
Specific gravity (SG)
Ratio of the weight of a material to the weight of an equal volume of water.
When is specific gravity used?
When identifying unknown gemstones or when distinguishing smaller gems.
