Transcript
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 propertiesdoubling 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 colorless sapphire
Pt triangles from crucible
Stress fractures 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 Found in peridot – Arizona origin Images from Barbara Smigel, http://www.bwsmigel.info/Lesson5 /DE.Magnification.html
Horsetail like inclusions curving asbestos fibersmineral bryssolite in Demantoid garnet Russian origin
Surface & Interior Features can ID Dendritic Chalcedony>
Natural ruby-multiple fingerprints
Unpolished girdle with “natural”
Surface reaching fracture
Elephant Ivory
Stab in heart (above) Single inclusion (below) Columnar & chicken wire-prove “man-made” reflected many times. opal
“Fingerprints” tsavorite Fibrous hematite in strawberry quartz
Bubbles in moldavite Bubble in CZ (below)
Natural ruby curved Straight color zoning –natural sapphire
< Rough diamond with internal fracture
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
