Sphene
Sphene is calcium titanium silicate (CaTiSiO5). The mineral was first discovered in Hauzenberg in the Bavarian region of Germany in 1795. It was named titanite for its titanium content. The synonym, sphene, was introduced in…
Gem NotesRhodochrosite
Rhodochrosite is manganese carbonate (MnCO3). It forms a solid solution series with siderite (FeCO3) with iron substitution and with calcite (CaCO3) with calcium substitution. The name is from the Greek meaning “rose colored.” Rhodochrosite is…
Gem NotesAustralian Fire Opal
In the past, non-play of color orange to red “fire opal” was best known from its sources in Mexico. While Australian opal varieties such as black opal, white, opal, and crystal opal are from sedimentary…
Gem NotesMint Tourmalines from Afghanistan
Gemworld International recently received a parcel of rough and faceted light green tourmalines for analysis. The material was examined and the quality characteristics were recorded. The lot consisted of five faceted samples ranging from 5…
Gem NotesShell Pearls
Shell “pearls” are appearing in the market with greater frequency and, more importantly, with features that now mimic cultured pearls of commercial, midlevel and finer qualities. During the recent Northwest Gemological conference, Gemstar International’s Evie…
Gem NotesPearls of Wisdom
Gemworld International was recently contracted by a colleague hired to assess potential damage caused by floodwaters that breached the foundation of a local branch of a major bank in the Greater Chicago area. The bank’s…
Gem NoteseBay Sale of Yellow Moissanite as Diamond
When it comes to moissanite, we usually think of the colorless variety as a diamond substitute. While we certainly hope for full disclosure, there are times when an appraisal customer is informed that they have…
Gem NotesStrain in Diamond
Recently an experienced bench jeweler and custom designer submitted a diamond to Gemworld for a damage report. The diamond had apparently developed an eye visible break in the crown during an otherwise routine retipping job…
Gem NotesCo-Glass and Sapphire Composites
During a December trip to the 2012 GIT Conference in Bangkok, Thailand, the author purchased several blue stones claimed to be (Cobalt) Coglass filled sapphires. General observation seemed to confirm the blue sapphire color with…
Gem Notes