Gemstone Observation &

Magnification

By Susie Aber

2011-2012

Observation & magnification…

Online Syllabus with links to lectures

http://academic.emporia.edu/abersusa/go340/syllabus.htm

Gem Testing

http://academic.emporia.edu/abersusa/go340/gemtest.htm

Equipment …

Why magnify? What will I see?

• Appraisal – Insurance/ Cut - Polish & Repair :

• Identify, justify, & document gem/jewelry origins to properly

insure or claim

• evaluate/grade as to how fine or rare the piece is… determine

replacement/market value

• fingerprint the gem – plot on diagram facets & inclusions

• Identity by characteristic – origin/growth lines

optical properties-

doubling of back facet

Images from Barbara Smigel,

http://www.bwsmigel.info/Lesson5

/DE.Magnification.html

Why magnify? What will I see?

Justify authenticity – natural/synthetic, enhanced/treated?

Natural rutile silk Pt triangles Stress fractures

colorless sapphire from crucible from high heat

Gems too “clean” or with tiny metallic triangles of a uniform

appearance are usually synthetics… Sapphire is often

heated to get rid of the “silk” rutile… Images from Barbara Smigel, http://www.bwsmigel.info/Lesson5/DE.Magnification.html

Why magnify? What will I see?

Characteristic lily pad inclusions Horsetail like inclusions

Found in peridot – Arizona origin curving asbestos fibers-

mineral bryssolite in

Images from Barbara Smigel, Demantoid garnet -

http://www.bwsmigel.info/Lesson5 Russian origin /DE.Magnification.html

Images from Barbara Smigel, http://www.bwsmigel.info/Lesson5/DE.Magnification.html

Dendritic Chalcedony>

<Vanadinite Drusy

<Rutile Quartz

Images from Barbara Smigel,

http://www.bwsmigel.info/Lesson5

/DE.Magnification.html

Surface & Interior Features can ID

Why magnify… What will I see…

• Expect surprises with magnification! Imperfections are natural… • imperfections in colorless stones affect value negatively

• imperfections in colored stones may enhance value - aligned rutile needles create 6 rayed stars in ruby & sapphire…

• Internal imperfections and inclusions are • Solid, filled cavities/cracks/fissures & crystal growth patterns (color

zoning, banding, or swirls)

• Rainbow effect is internal crystal stress from external pressures- “feathers” can cause the gem to shatter

• External imperfections reflect quality of cut & polish • Symmetry of facets

• Out of round cabochon

• Chips, cracks, scratches

• Conchoidal fracture at drill hole can signify glass bead…

Observation & magnification…

Equipment …

A loupe is a “single lens”

magnifying device, which enlarges

objects to be viewed to ten times its

size (10x – 1 inch focal length). The

triple aplanatic or Hastings triplet is

a high quality lens made of two

external lenses of flint glass (or lead

glass) that is cemented to a double

convex crown glass. Flint glass is

composed of silica, soda, and a lead

oxide and is commonly used in

glass to imitate gems.

The visor fits on head

and allows both

Hands to be free. The

magnification is

Usually 3.5X – 4 inch

focal length.

Observation & magnification…

Binocular stereoscopic

microscope – ocular or eyepiece lenses,

there is an objective lens, which creates

a two lens system to produce a enlarged

sharp image. Magnification is calculated

by multiplying the objective and ocular

magnification (e.g., a 10X objective and

3X ocular produces a magnification of

30 times. Gem microscopes create a

"reinverted" image (regular compound

microscopes invert the image) and

usually have a zoom feature to vary the

magnification. Fluorescent light source

overhead; high intensity light transmitted

up from base.

Maglite shining up

through stone & eye

Looking down through

low magnification

at a comfortable distance!

With microscope – light from bottom:

brightfield for color zoning, dye concentration/

darkfield to highlight internal features

Images from Barbara Smigel,

http://www.bwsmigel.info/Lesson5

/DE.Magnification.html

Same gem –

reflected light from above

darkfield light from below

Images from Barbara Smigel,

http://www.bwsmigel.info/Lesson5

/DE.Magnification.html

Unpolished girdle

with “natural”

Elephant Ivory

Surface reaching fracture

Non-surface

Reaching

Feather in

Tourmaline>

Natural ruby-multiple

fingerprints

Columnar & chicken

wire-prove “man-made”

opal

Stab in heart (above)

Single inclusion (below)

reflected many times.

Fibrous hematite

in strawberry quartz

Diamond in diamond>

< Rough diamond

with internal fracture

Bubbles in moldavite

Bubble in CZ (below)

“Fingerprints” tsavorite

Natural ruby curved

<Straight growth-synthetic flux

Straight color zoning –natural sapphire

Key Steps in Examining a Stone…

• Best to examine unmounted stones

• Be sure gem is free of dirt & dust

• Hold the unmounted transparent stone by girdle

• View under proper lighting • surface features – light source from above

• internal features – light source coming up through

the stone

• Rotate the stone to view at different angles (be

sure you are not looking at the tweezers!)

• Shift stone towards you and away- focusing on

surface and interior

Loupe & observations…

• Hold the loupe to your eye and brings stone close

until in focus

• Have light source from top and side with dark non-reflective

background (dark-field illumination) – with faceted stone

look through pavilion & rarely through table, which can

show the culet but obscures the interior of the stone

• Focus eye on feature and surface – if both in focus the

feature is on the surface; otherwise the feature is below

the surface.

• Observe cut proportions & symmetry of gems and surface

& interior features

This week – online lectures in review…

Gem Lore

http://academic.emporia.edu/abersusa/go340/gemlore.htm

Gem Origins

http://academic.emporia.edu/abersusa/go340/origins.htm

Agate & Chalcedony

http://academic.emporia.edu/abersusa/go340/chalcedo.htm

Gem Briefs

http://academic.emporia.edu/abersusa/go340/gembrief.htm