Surface Features

Surface features are characteristics found at or near the polished surface of a
gemstone (technically blemishes rather than inclusions, though the distinction blurs
when a feature extends inward). They carry independent diagnostic information about
authenticity, treatment history, and durability. The most gemmologically significant
are naturals and trigons: a natural is a remnant of the original crystal surface
left by the cutter to preserve weight, confirming natural crystalline origin since
no synthetic material carries a genuine growth surface. Trigons (tiny triangular
growth pits or raised pyramids on diamond octahedron faces) are oriented opposite
to the crystal face and are diagnostic of natural diamond, absent from all synthetic
productions ^[1]. Further down the significance scale, bearding
(fine fractures from bruting), extra facets, laser-drill holes, and surface graining
all provide evidence about cutting history and treatment status. In practical
assessment, reflected-light examination of the girdle at 10–40× is the fastest way
to identify many of these features before committing to immersion or spectroscopy.

Naturals are remnants of the original crystal surface left on a cut gemstone
^[1]:

Characteristics:

• Original rough crystal surface preserved
• Usually found on or near the girdle
• May show trigons (triangular growth marks) ^[1]
• Often left deliberately to preserve weight

Significance:

• Proves natural origin (synthetics don't have naturals) ^[1]
• Acceptable in diamond grading if confined to girdle
• Should not affect face-up appearance

Bearding consists of tiny fractures along the girdle, created during cutting
^[2]:

Formation:

• Created by the bruting (girdling) process
• Mechanical stress causes minute fractures
• Extends from girdle into stone interior

Appearance:

• Hair-like fractures at girdle edge
• Creates "fuzzy" or "fringed" appearance
• Severity ranges from minor to extensive

Grading impact:

• Minor bearding often acceptable
• Heavy bearding can affect clarity grade
• May be reduced by re-polishing girdle

Extra facets are small additional polished surfaces not part of the standard cut:

Purposes:

• Remove surface-reaching inclusions
• Eliminate naturals or damage
• Correct cutting errors

Location:

• Often on pavilion near girdle
• May be on crown
• Should not be visible face-up (ideally)

Grading consideration:

• Generally considered a blemish
• Impact depends on visibility
• Very common in coloured stones

Surface graining appears as visible growth lines on polished surfaces:

Types:

• Whitish graining - Light-coloured lines
• Reflective graining - Shiny, mirror-like lines
• Transparent graining - Subtle lines, often internal origin

Relationship to internal graining:

• Surface graining often continues internally
• Represents structural irregularities
• Related to crystal growth conditions

Etch features result from natural dissolution processes ^[1]:

Etch channels:

• Tube-like cavities extending from surface
• Created by corrosive fluids during geological history
• Often follow crystallographic directions
• Can contain secondary minerals

Etch figures:

• Geometric depressions on crystal faces
• Reflect underlying crystal symmetry
• Trigons on diamond octahedron faces (triangular etch pits) ^[1]
• Hexagonal pits on corundum

Laser drilling is a treatment that creates access channels to internal inclusions:

Purpose:

• Access dark inclusions for bleaching
• Improve apparent clarity

Appearance:

• Very fine, straight channels
• May appear as tiny dots on surface
• Often lead to bleached inclusion sites
• Visible under magnification

Detection:

• Look for unnaturally straight tubes
• Follow tube to inclusion site
• May show surface opening