Ethiopian Opal
Since reemerging in the market after a decade long hiatus, opal from Ethiopia has generated a lot of buzz during the past six years. Anyone visiting a major gem show since 2009 has likely seen…
Gem NotesVesuvianite
Introduction: Vesuvianite is a tetragonal mineral with the formula Ca10Mg2Al4(SiO4)5(Si2O7)2(OH)4. As the name implies, it was named after the locality of its discovery, Mount Vesuvius, Campania, Italy. It has an interesting history in the nomenclature…
Gem NotesSphalerite
Introduction: Sphalerite is zinc sulfide (ZnS), also known as zinc blende. It is a fairly common mineral crystallizing in the isometric system and is a principal ore of zinc. In addition, it often contains iron…
Gem NotesGem Note: Hauyne
Introduction: Haüyne is an extremey rare mineral, a member of the sodalite group, and is even more rare as a gemstone with the formula (Na,Ca)4-8Al6Si6(O,S)24(SO4,CL)1-2. It is sometimes seen in the literature as hauyne or…
Gem NotesSerendibite
Introduction: Serendibite is an extremely rare mineral with the chemical formula Ca2(Mg,Al)6(Si,Al,B)6O20. The mineral was first discovered in 1902 by G.T. Prior and A.K. Coomaraswamy at Gangapitiya, which is near Ambakotte, approximately 12 miles (20 km…
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 Notes