Assignment 10 - Clarity Flashcards
Characteristic or irregularity confined to the surface of a polished gemstone.
Blemish
How do inclusions and blemishes affect gemstone durability?
Some inclusions can affect durability. Breaks in a stone can threaten its structural integrity, especially if they reach the surface.
How do inclusions and blemishes affect gemstone appearance?
They can have a dramatic effect on appearance. Some can reduce brilliance by disrupting the transmission of light through a gem.
The term inclusion can have negative meanings for some, but inclusions can contribute to the beauty of colored gemstones.
How do inclusions and blemishes affect gemstone value?
Although they might affect appearance or durability, inclusions and blemishes seldom have a significant impact on a colored stone’s ultimate
value. Clarity characteristics that affect transparency and brilliance, or those that make a gem vulnerable to breaking, have the most influence on value.
What are ten commonly seen inclusions?
- Included crystal & Negative crystal
- Needle & Silk
- Fingerprint & Feather
- Pinpoint & Cloud
- Cavity & Chip
What are three commonly seen blemishes?
- Scratch
- Abrasion
- Polish lines
A mineral crystal trapped within a gem as it grows.
Included crystal
An angular, hollow space within a gem that resembles a mineral inclusion.
Negative crystal
A long, thin inclusion that can be a solid crystal or a hollow tube that might be filled with liquid or gas.
Needle
Group of fine needle-like inclusions.
Silk
Inclusions that form a pattern that often resembles a human fingerprint.
Fingerprint
A general term for a break in a stone.
Feather
Any hazy or milky area that cannot be described as a feather, fingerprint, or group of included
crystals or needles.
Cloud
Minute inclusion enclosed within a gem; can occur singly or in groups called clouds.
Pinpoint
An opening that extends into a gem from the surface.
Cavity
A damaged area on a gem, usually near the girdle.
Chip
A linear scrape, normally seen as a fine curved or straight white line.
Scratch
Tiny nicks and pits caused by wear and damage to a gem’s facet edges or culet.
Abrasions
Tiny, parallel grooves on a facet surface left by the polishing operation.
Polish lines
What factors determine a clarity characteristic’s influence on gem value?
- nature
- size
- number
- position
- relief
What are the levels of clarity for colored stones?
1) Eye-clean
– no visible inclusions
2) Slightly included*
– Type I : minute inclusions
– Type II: minute or minor inclusions
– Type III: minute, minor or noticiable inclusions
3) Moderately included*
– Type I: minor inclusions
– Type II: noticiable inclusions
– Type III: obvious inclusions
4) Heavily included
– Prominent inclusions with negative effect on appearance, durability and value
5) Severely included
– Prominent inclusions with severe effect on appearance, durability and value
*Definition varies between Type I, II and III stones
Contrast between an inclusion and its host gem.
Relief
What are the three types (categories) of gem stones with respect to their typical clarity?
- Type I (typically eye-clean) - aquamarine; pink, green, and yellow beryl; chrysoberyl (excluding cat’s-eye); spodumene; green tourmaline; blue
zircon; and tanzanite. - Type II (typically visible inclusion that don’t affect beauty), anadusite, alexandrite, corundum (excluding stars), the transparent garnets, iolite, peridot, spinel, quartz, all colors of tourmaline except green and water-melon, and zircon.
- Type III (almost always included) - emerald, red beryl, and watermelon tourmaline.
Why is your unaided eye an important tool for colored stone grading?
- Clarity characteristics that cannot be detected by the unaided eye will unlikely have a negative impact on the value of a colored stone.
- You might not have time to examine a stone with an instrument
When might you use a loupe to judge an individual stone?
You should take the time to examine
expensive stones carefully with a loupe.
How do you judge the clarity of gemstones in parcels?
- evaluate its consistency of color, cut, clarity, and size. (don’t buy mixed or uncalibrated parcels)
- take a sample selection and quickly look at color, brilliance, clarity, calibration, face-up outline, and pavilion depth.
- assess value of parcel.
Which of these clarity characteristics usually have the greatest impact on a gem’s marketability?
A. A cavity on its pavilion
B. A large, unhealed feather under its table
C. A small, dark crystal under its crown facets
D. A low-relief liquid inclusion under its table
B. A large, unhealed feather under its table
Fingerprints are
A. pits.
B. fractures.
C. blemishes.
D. partially healed fracture planes.
D. partially healed fracture planes.
Gems that are usually eye-clean include
A. peridot, spinel, and quartz.
B. ruby, alexandrite, and andalusite.
C. spodumene, yellow beryl, and aquamarine.
D. red beryl, emerald, and watermelon tourmaline.
C. spodumene, yellow beryl, and aquamarine.
Growth zoning in a colored stone is evidence of
A. fashioning.
B. heat treatment.
C. crystal growth.
D. fracture filling.
C. crystal growth.
