GI-2: General Observation

Question 1

Transparent

Answer 1

Description of a material that’s capable of transmitting light so objects viewed through it appear clear and sharp.

Question 2

Translucent

Answer 2

Description of a material that’s capable of partially transmitting light so an image seen through it appears obscure, with a vague outline.

Question 3

Opaque

Answer 3

Description of a material that’s unable to transmit light, so an image can’t be seen through it.

Example: Turquoise

Question 4

Luster

Answer 4

The appearance of a material’s surface in reflected light.

Depends on material’s RI, hardness, quality of polish.

Question 5

What is the most common luster for transparent stones?

Answer 5

Vitreous

Question 6

Cleavage

Answer 6

A smooth, flat break in a gemstone parallel to places of atomic weakness

Example: Calcite with 3 directions of cleavage

Question 7

Parting

Answer 7

A flat break in a gemstone parallel to a twinning plane

Question 8

Fracture

Answer 8

Any break in a gem other than cleavage or parting

Question 9

Conchoidal fracture

Answer 9

A curved and ridged fracture in a gemstone, extending from the surface inward.

Examples: Glass

Question 10

Splintery Fracture

Answer 10

A gemstone fracture looks lke broken wood, resulting from the fibrous structure of certain gems

Examples: Hematite and tiger’s eye quartz

Question 11

Fire

Answer 11

The flashes of spectral color you see in a polished gem, especially a diamond

Is much easier to assess in colorless gems than in those with strong bodycolor

Question 12

Dispersion

Answer 12

The separation of white light into spectral colors.

Is measured with RI.

Is a property that remains constant no matter how a gem material is fashioned.

Question 13

What are the 3 types of surface breaks in a stone?

Answer 13

1. Cleavage
2. Parting
3. Fracture

Question 14

Heft

Answer 14

How heavy an object feels in relation to its size.

Gives an indication of physical density or specific gravity

Grades: High, Moderate, Low

Question 15

What are the 2 primary ways to detect assembled stones?

Answer 15

1. Magnification

and

2. Reflected light (red ring test)

Question 16

Where is best place on stone to judge transparency?

Answer 16

Where the stone transmits the most light

Question 17

Where is the best place to judge luster?

Answer 17

On the surface area that has the best polish.

Question 18

When a material only partially transmits light so that an image seen through it has just a vague outline, it is described as

Answer 18

Translucent

Question 19

What is Asterism caused by?

Answer 19

Reflections from precisely oriented, needle-like inclusions

Question 20

You should start the gem identification process with

Answer 20

General Observation

Question 21

The cat’s-eye effect is also called

Answer 21

Chatoyancy

Question 22

If you see a red ring during your examination of a gem it is an

Answer 22

Garnet-and-Glass doublet

Question 23

If you have a gem where a design is engraved into the surface, record its cutting style as

Answer 23

Intaglio

Question 24

If you observe extreme fire in a colorless gem, it might be

Answer 24

Synthetic Rutile

Question 25

Heft cannot be tested on a gem if it is

Answer 25

Mounted

Question 26

The degree to which a material transmits light is its

Answer 26

Transparency