Assignment 9 - Cut

Question 1

The angles and relative measurements of a polished gem, and the relationships between them.

Answer 1

Proportions

Question 2

What properties of the rough determine how the stone is fashioned?

Answer 2

Quality: intensely colored ruby rough can produce cut stones of superb face-up color even if their proportions are less than ideal, or the finished gems are small.

Transparency: Usually, cutters only facet transparent rough. Translucent and opaque gems don’t benefit much from faceting.

Inclusions: Some gemstones have many cracks and fissures. Emeralds, for instance, are commonly fractured due to the way they form in the earth. The mining and recovery process might also cause some damage. It’s easy to remove shallow fractures, but deep fractures can limit the shape of the finished gem, and heavily fractured areas might need to be removed entirely. The rough might even split into two or more pieces, forcing the cutter to consider them separately.

Color distribution: In the most desirable rough, the color is distributed evenly throughout the stone. Unfortunately, this is very rare, and many gems have uneven color distribution. For example, sapphire and amethyst rough commonly contain strong bands of color parallel to the crystal faces. If the cutter isn’t careful, this color zoning might be visible enough to negatively affect the beauty of the finished stone.

Question 3

How do a cutter’s decisions balance beauty and economics?

Answer 3

High end. Size > beauty.
Middle: Beauty > Size
Low end: cheap labour

Question 4

What are the steps in the cutting process?

Answer 4

0) selecting suitable rough
1) sort the rough by size
2) cobbing to remove included material
3) sawing
4) grinding
5) preform
(wait for order)
6) faceting
7) polishing

Question 5

What’s the most crucial cutting stage?

Answer 5

The preform stage has the greatest impact on the value of the finished gem, so it requires the attention of highly skilled workers.

Question 6

Removing heavily included sections from gemstone rough by carefully tapping it with a small hammer.

Answer 6

Cobbing

Question 7

Dividing gem rough into easily handled pieces and removing waste areas.

Answer 7

Sawing

Question 8

Giving approximate shape to a gemstone, or producing flat planes for polishing facets.

Answer 8

Grinding

Question 9

Top part of the gem above the girdle.

Answer 9

Crown

Question 10

Facet at the top of the crown, usually the largest facet on the stone.

Answer 10

Table facet

Question 11

Lower part of a faceted gem below the girdle.

Answer 11

Pavilion

Question 12

Narrow section that forms the boundary between the crown and the pavilion, and functions as the gem’s setting edge.

Answer 12

Girdle

Question 13

Rough ground to the approximate shape of the finished stone; also, the act of producing this
shape.

Answer 13

Preform

Question 14

Wooden or metal stick that holds the preform during faceting.

Answer 14

Dopstick

Question 15

Horizontal spinning metal disk used to grind or polish a gem’s facets.

Answer 15

Lap

Question 16

Device that holds the dopstick at precise angles to allow correct orientation during faceting
and polishing.

Answer 16

Faceting head

Question 17

Final stage in gem cutting
that produces the smoothest
possible surface.

Answer 17

Polishing

Question 18

The arrangement of a stone’s facets.

Answer 18

Style

Question 19

Cutting style with triangular or kite-shaped facets that radiate from the center toward the girdle.

Answer 19

Brilliant cut

Question 20

Cutting style with mainly square and rectangular facets arranged in concentric rows.

Answer 20

Step cut

Question 21

A cutting style that combines brilliant-cut and step-cut facets.

Answer 21

Mixed cut

Question 22

A smoothly rounded polished gem with a domed top and a flat or curved base.

Answer 22

Cabochon

Question 23

A gem carving style in which the design, often a woman’s profile, projects slightly from a flat or curved surface.

Answer 23

Cameo

Question 24

A design engraved into the surface of a gemstone.

Answer 24

Intaglio

Question 25

Artistic gem cuts that aren’t limited to specific proportions or shapes.

Answer 25

Designer cuts

Question 26

A free-form cut that can feature alternating curved and flat surfaces.

Answer 26

Fantasy cut

Question 27

Light that eventually returns to the eye after entering a gem through the crown, reflecting off
its pavilion facets, and exiting back through the crown.

Answer 27

Brilliance

Question 28

How do differences in pavilion depth affect a gem’s appearance?

Answer 28

Flat stones with shallow pavilions usually have areas of lower color intensity, called windows.

You’ll usually see dark areas, or extinction, through the crown in stones with deep pavilions.

Question 29

How do you examine a gem to judge its brilliance?

Answer 29

Clean the stone, then pick it up with tweezers by its girdle. Look at the stone face-up and estimate the percentage of the stone’s entire surface that returns light to your eye. Make sure you ignore any surface reflections. Also remember that even well-cut gems can show some windowing and extinction at certain viewing angles. Rock the stone back and forth, but don’t tilt it any more than 30 degrees or so.

> 75%: excellent.
60-75%: very good.
40-60: pretty good.
25-40%: there’s substantial light leakage, and this will detract from the attractiveness of the stone.
<25%: The stone has very serious proportion problems. Most of the light was lost through the pavilion facets.

Question 30

Which proportion problems are the most serious?

Answer 30

Lack of symmetry as well as excessive depth or shallowness.

Question 31

How is a stone’s symmetry judged?

Answer 31

When you consider the symmetry of a cut gem, you assess its shape from above—the face-up position—and from the side—the profile position.

Question 32

Which three factors do you consider when assessing a gem’s finish?

Answer 32

• quality of the surface condition or polish
• symmetry
• number and placement of its facets

Question 33

How do you put a stone’s qualities together to evaluate cut?

Answer 33

Overall assessment of:
- Brilliance
- Face-up symmetry
- Profile symmetry
- Ratios (length-to-width, table to pavillon)
- Bulge/girdle thickness
- finish (polish, symmetry and facets)

Question 34

The precision and balance of the corresponding parts of a finished gem.

Answer 34

Symmetry

Question 35

The relationship of the height of a gem’s crown to the depth of its pavilion, judged by viewing its profile.

Answer 35

Crown-height to pavilion-depth ratio

Question 36

Which colored stone variety has cutting challenges due to vulnerable cleavage planes?

Answer 36

Topaz, spodumene and tanzanite.

Question 37

Excessive bulge on a step cut

A. adds weight.

B. adds beauty.

C. increases brilliance.

D. makes mounting easier.

Answer 37

Excessive bulge on a step cut

A. adds weight.