Georgia is not characterized by a great variety of jeweler gem deposits but the existing manifestations of agate, opal and obsidian are distinguished by picturesque texture and very good jeweler properties. Two main deposits of agate (Akhaltsikhe in the Ajara-Trialety subterrane and Dmanisi in the Somkhito-Karabakh terrane; for getting Geological & Metallogenic Framework, please,
here) are related to fault structures in Eocene volcanic sequences filled by opal-chalcedony hydrothermal matrix. Agate forms numerous nests (their mass is often several kg) of red, rose, pink, blue colors and thin-layered structure. Bulk reserves are over 3 millions kg. Obsidian from the Kayundag deposit (a Neogene ryolite flow) has excellent technical characteristics for different kinds of art and jeweler productions.
Four-Layer Agate at the Akhaltsikhe Mine. A. Tvalchrelidze Mineralogical Museum, I. Javakhishvili Tbilisi State University
Independently a unique geological phenomenon - the Goderdzi deposit of opalized wood must be mentioned (Adjara-Trialeti subterrane).
Accumulation of wood was determined by shallow-water bog sedimentation buried under Late Neogene andesitic pyroclastics. Mineralization represents practically a pseudomorphosis of opal upon the wood branches and trunks. Opalization occurred due to rapid dyagenetic and autigene alteration under influence of postvolcanic hydrothermal SiO2 supply. The 600-m-thick opal-bearing sequence extends on 15 km covering an area of 85 km2. Entirely opalized wood trunks often form large accumulations. The texture of yellow to dark brown and even black opal repeats in every detail primary composition of the replaced wood. Opal has magnificent decorative properties but the deposit must be exploited very carefully in course of protection of this natural phenomenon. Recently the Georgian parliament decided to create a national park.
In addition to these gems gagate occurrences should be mentioned. All of them are encountered among seams of the Tkibuli-Shaori Mine. Traditionally Georgian artist in national jeweler masterpieces largely used gagate.
Opal in Petrified Wood of the Goderdzi Deposit. A. Tvalchrelidze Mineralogical Museum, I. Javakhishvili Tbilisi State University
Gagate of the Tkibuli-Shaori Mine. A. Tvalchrelidze Mineralogical Museum, I. Javakhishvili Tbilisi State University