Ass #9 : Clarity and Examination Techniques

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Questions and Answers

What is considered a clarity characteristic in gemstones?

The overall size of the gemstone

Blemishes on the surface (correct)

The carat weight of the stone

Color variations within the stone

What type of loupe is recommended for examining gemstones to avoid distortion?

Triplet loupe corrected for color and linear distortion (correct)

Single element loupe with no corrections

Plastic magnifying glass

Standard glass loupe

Which type of characteristic is a crystal (Xtl) found within a diamond classified as?

Surface feature

Refraction artifact

Blemish

Inclusion (correct)

How is a blemish different from an inclusion when grading clarity?

Blemishes are surface features, while inclusions are internal Signup and view all the answers

What illumination technique is most effective for making inclusions stand out clearly during examination?

Darkfield illumination Signup and view all the answers

What characteristic of a bruise in a diamond is notable at 10x magnification?

It shows tiny root-like feathers. Signup and view all the answers

Which of the following statements about a knot in a diamond is true?

It can cause polishing delays due to its orientation. Signup and view all the answers

What change occurs to a patch of color due to the heat of the cutting process?

It turns brown. Signup and view all the answers

What is the main indication that a chip on a diamond might be present?

It is located at the girdle edge or facet junction. Signup and view all the answers

What is the purpose of internal laser drilling in diamonds?

To expand a pre-existing feather around a dark inclusion. Signup and view all the answers

How can the presence of a fracture filling treatment be identified?

By the flash effect when tilted. Signup and view all the answers

What is the definition of a cavity in the context of diamond inclusions?

An opening caused by crystal loss during polishing. Signup and view all the answers

Where is a nick typically found on a diamond?

Near the girdle edge or facet junction. Signup and view all the answers

What is the appearance of a twinning wisp in a diamond?

Flat and ribbon-like, radiating from the diamond's center Signup and view all the answers

What distinguishes cleavage from a feather in diamond inclusions?

Cleavage occurs in a specific cleavage plane, while feathers can break in any direction Signup and view all the answers

How does internal graining affect a diamond's clarity grade?

Colorless or transparent internal graining has no effect on the clarity grade Signup and view all the answers

What can a grain center in a diamond appear like?

A small area with thread-like or pinpoint-like appearance Signup and view all the answers

What characteristic does a bearded girdle exhibit?

Minute or minor feathers running perpendicular to a bruted girdle Signup and view all the answers

What typically causes the appearance of clouds in diamonds?

Many tightly grouped pinpoints that resemble light haze or dense patches Signup and view all the answers

What kind of appearance does an etch channel have?

An angular opening that can be either straight or curved Signup and view all the answers

What is the visual effect of heavily bearded girdles on diamonds?

They create a fuzzy gray fringe around the perimeter of the stone Signup and view all the answers

In terms of grading, what is the main issue with clouds in a diamond?

They can reduce the diamond’s transparency and brilliance Signup and view all the answers

What common characteristic do feathers and cleavage share?

Both are considered surface reaching inclusions Signup and view all the answers

What is the appearance of an abrasion on a diamond's surface?

A series of minute scratches or pits Signup and view all the answers

What causes a burn on a diamond's surface?

Excessive heat during polishing Signup and view all the answers

How does a pit form on a diamond's surface?

When pinpoint inclusions are pulled during polishing Signup and view all the answers

What defines an extra facet on a diamond?

A facet not required by the cutting style Signup and view all the answers

What is a polish mark in diamond grading?

A feature that lacks a distinct facet junction Signup and view all the answers

Which condition is characterized by a wavy or bumpy area on a diamond's surface?

Lizard skin Signup and view all the answers

What indicates a rough girdle on a diamond?

An irregular, pitted surface Signup and view all the answers

Which of the following is a characteristic resulting from laser manufacturing?

A laser manufacturing remnant Signup and view all the answers

What is a dop burn in diamond polishing?

A hazy area caused by heat where the dop touches the diamond Signup and view all the answers

Identify the feature that appears as a thin, dull white line on a diamond's surface.

Scratch Signup and view all the answers

Study Notes

Clarity Grading

Clarity grading is a key aspect of GIA's grading system.
Clarity characteristics are often called flaws or imperfections.
Two types:
- Inclusions: features inside a gemstone, or extending from the surface.
- Blemishes: surface-confined features.

Examining Stones

Examine with a jeweler's loupe (10x) or binocular microscope.
Use a triplet loupe (color and linear distortion corrected)
Chromatic aberration: rainbow effect around the viewing field.
Spherical aberration: straight lines appear to bend at edges.
Achromatic and aplanatic lenses correct these distortions.
Darkfield illumination shows inclusions.
Brightfield illumination shows them as black objects.
Depth of field: area in focus; smaller with increased magnification.
Prism images: multiple images of a characteristic due to diamond's refraction.
Light source angle distinguishes between surface and internal characteristics.

Types of Clarity Characteristics

Internal Inclusions: mineral crystals (over 24 types identified).
- Needle: thin, rod-like crystal (white, bright, or dark).
- Pinpoint: tiny, dot-like crystal (mostly white, sometimes dark).
- Cloud: tightly grouped pinpoints (may be misty, gray, or dense).
- Twinning wisp: radiating pinpoints, clouds, or crystals in a twinning plane. Looks ribbon-like.
- Internal graining: irregular crystal growth (lines, angles, streak-like, colored or transparent).
- Grain center: small, focused area of growth distortion, white or dark.
Surface-Reaching Inclusions:
- Feather: general term for any break.
- Etch channel: angular opening in the surface, often with striations perpendicular to length.
- Bruise: area of impact with tiny feathers.
- Knot: a slightly raised included crystal extending to the surface.
- Patch of color: natural radiation stains (originally green, can turn brown).
- Chip: shallow opening.
- Cavity: opening from a feather break or crystal ejection.
- Indented natural: a portion of the original surface.
- Laser drill-hole: tunnel created by a laser beam.
- Internal laser drilling: expands or creates a feather around a dark inclusion.

Blemishes

Rough girdle: irregular, pitted, or granular surface.
Pit: small white dot.
Laser manufacturing remnant (LMR): markings during laser manufacturing creating internal or surface fractures.
Natural: part of the rough diamond's original surface (skin).
Surface graining (SG): visible crystal structure lines on a facet.
Nick: a small notch on a facet.
Abrasion: scratch marks.
Scratch: thin line.
Extra facet: an unplanned facet.
Polish mark: bumpy/wavy surface area.
Lizard skin: wavy or bumpy area on surface
Burn(Brn): hazy surface from excessive heat from polishing

Other Features

Inscriptions: text, numbers, or logos (surface only).
Surface grooves for invisible mounting.

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Description

This quiz explores the clarity grading of gemstones, focusing on inclusions and blemishes. It covers methods for examining stones using various tools and the effects of different types of lenses. Test your knowledge on clarity characteristics and their visual effects in gemstone assessment.