Stone Information - Chalcedony (Quartz) PDF

****Chalcedony (Quartz) ***** LARGEST CONSUMERS : Treated Black Chalcedony is sold more then any other chalcedony variety, Agate is a favorite amongst collector and consider the first gem used for personal adornment , Iris Agate is one the most valuable chalcedony varieties MOHS SCALE: 7 VARIETY/SPE...

****Chalcedony (Quartz) ***** LARGEST CONSUMERS : Treated Black Chalcedony is sold more then any other chalcedony variety, Agate is a favorite amongst collector and consider the first gem used for personal adornment , Iris Agate is one the most valuable chalcedony varieties MOHS SCALE: 7 VARIETY/SPECIES/GROUP: Quartz COLOR/HUE RANGE/VALUE: chalcedony in its purest form is white to milky gray Chrysoprase: finest color is the light to medium yellowish green, semitransparent to translucent, apple green to a medium to dark saturated green, can also be green to bluish green color Chrysocolla-in-chalcedony: translucent to semitranslucent, intense light blue or blue-green gem resembles fine turquoise Carnelian & Sard: semitransparent to translucent and ranges from yellowish orange through orangy red to brownish orange Sard is semitransparent to translucent, dark reddish brown to dark orange-brown Onyx: parallel stripes/bands of contrasting colors, parallel stripes of contrasting colors Sardonyx: patterned with white or black bands alternating with reddish brown bands Treated Black Chalcedony: chemically treated gray chalcedony (Natural black chalcedony is rare) Blue Chalcedony: light grayish blue to bluish gray,light to medium blue tinged with violet, with weak adularescence Jasper: opaque chalcedony variegated or display straight color bands of typically brownish reds, yellows, and blacks Bloodstone: type of jasper with red to brownish red fleck scattered over across a dark green background Agate: eye-visible banded markings that vary in color and transparency with growth band that follow that contours of the cavities, different names are given to certain types based on there variations in banding Iris Agate: semitransparent to translucent and shows iridescent colors Chinese Red Agate: intense red, white, or grayish color bands Fire Agate: brownish bodycolor with vivid red, green, and gold spectral colors CHEMICAL COMPOSTION: silicon and oxygen, common trace element is iron oxide Chrysoprase: trace element is nickle, or chromium (when greenish blue) Treated Black Chalcedony: after treatment carbon is left creating the black color Jasper & Bloodstone: trace elements of iron oxides Chinese Red Agate: trace element iron FORMING SOURCE: pegmatite and volcanic and sedimentary rocks Agate: forms inside gas cavities in volcanic rocks, often, the concentric rings don’t completely fill the cavities, leaving a hollow center lined with quartz crystals creating geodes Fire Agate: inside cavities as a botryoidal growth made up of flat crystals of an iron mineral over layers of chalcedony COMMON TREATMENTS: Chrysoprase: grayish chalcedony would be soaked in a mixture of water, acid, and chromium or nickel compounds, and then heated and dried, and marketed as "green agate" or "green onyx" Chrysoprase: dyed to improve hue Treated Black Chalcedony: gray chalcedony is soaked in a sugar solution and then boiled in sulfuric acid Blue Chalcedony: heated to a milky white and then dyed in an array of colors,dyed to create a deeper blue Jasper: dye blue to resemble lapis lazuli, Agate: typically dyed ( affects depend on how porous certain layers are), heat treatment is also common to get orange or orangy red from yellow and brown material CRYSTAL STRUCTURE: cryptocrystalline quartz- aggregates of tiny microscopic crystals, ability to produce "botryoidal" crystal growth habit is a gem begins inside cavities and has a bumpy appearance similar to a bunch of grapes POSSIBLE PHENOMENA: Iris Agate: iridescent colors Fire Agate: thin regular layers of iron mineral goethite create iridescent colors CLARIETY CHARACTERISTIC: chrysoprase is heated or exposed to sunlight, its color fades. COMMON CUTS: Chrysoprase: cabochon or carved or inlay Carnelian: cabochons or beads and intaglios Onyx and Sardonyx: Cameos, Carved relief Treated Black Chalcedony: cabochons, tablets, or beads Blue Chalcedony: cabonchon Iris Agate: Sliced or carved designs Chinese Red Agate: Carved on a small and large scale, cabochons and beads Fire Agate: due to the irregularity of the iridescent layers they are cut into unique cabonchons TRADES NAMES: Chrysoprase: “golden apple” , “Aquaprase" is bluish green from Africa Blue Chalcedony: “moonstone” or “blue moonstone” mistaken often for the true feldspare versions Jasper: treated jasper is called "blue onyx" or "Swiss lapis" Chinese Red Agate: southern red agate COUNTRIES OF ORIGIN: Chrysoprase: Queensland Austrialia(apple Green), Brazil(olive green), Tanzanian(yellowish green),India, the Czech Republic, Slovakia, and the US. Chrysocolla-in-chalcedony: US Keystone Copper Mine near Globe, Arizona, Mexico, Israel Carnelian & Sard: Brazil, India, and Uruguay Onyx and Sardonyx: Brazil, Madagascar, the US, and Uruguay Treated Black Chalcedony (gray Chalcedony): Brazil Blue Chalcedony: California’s Mojave Blue, US states of Oregon and Washington, Namibia and Turkey Bloodstone: Australia, Brazil, China, India, and the US Agate: Mexico, Brazil, and Uruguay. Other sources include India, Madagascar, China, and the US Iris Agate: Mexico and the US states of Texas and Oregon Chinese Red Agate: southern China, including Yunnan and Sichuan provinces and some areas along the Yangtze River Fire Agate: Mexican state of San Luis Potosi. Fire agate is also found north of Guadalajara, in the state of Jalisco, Mexico MAIN SYNTHETIC PROCESS: n/a COMMON IMITATION MATERIAL: Blue Chalcedony: glass (which is marketed in Taiwan) CUTTING/TRADING CENTER: Onyx//Saroynx: Idar-Oberstein, Germany, is a major manufacturer of chalcedony cameos and carvings