Stone Info Topaz & Beryl PDF
Document Details
Uploaded by ComplementaryLutetium
Gemological Institute of America
Tags
Summary
This document provides information about various types of gemstones, specifically topaz and beryl. It details their colors, properties, chemical compositions, and origins. The document also describes common treatments and cutting methods.
Full Transcript
*****Topaz & Beryl **** LARGEST CONSUMERS : Topaz: consumers in eastern Asia prefer shades of pink and red, USA market like all colors, especially blue, Europe prefer light yellow while Japan & German prefer Imperial topaz Aquamarine:China best market, along with Japan, Europe,Germany, Italy, US Mor...
*****Topaz & Beryl **** LARGEST CONSUMERS : Topaz: consumers in eastern Asia prefer shades of pink and red, USA market like all colors, especially blue, Europe prefer light yellow while Japan & German prefer Imperial topaz Aquamarine:China best market, along with Japan, Europe,Germany, Italy, US Morganite (Pink Beryl): China, and US consumers via TV MOHS SCALE: N/A VARIETY/SPECIES/GROUP: Aquamarine: Beryl variety COLOR/HUE RANGE/VALUE: Topaz: most commonly colorless, red, pink, purple, yellow, orange, and brown, as well as blue and green, colorless, Red and pink topaz varieties are rare & highly cherished, "Imperial Topaz " is the most valuable, red topaz is rare and most desired, pink topaz resembles pink diamond, golden or yellow are the least valuable Imperial Topaz: medium reddish orange to orange-red color however yellowish orange, orangy yellow, or yellow gems that show slightly purplish red to reddish orange pleochroism face-up is another description Blue Topaz: Heat treated to establish color, many shades of blue, dealers use terms like “London blue,” “Swiss blue,” “super blue,” and “maxi blue” to describe darker blues, and “sky blue” for paler hues Aquamarine: blue, very slightly greenish blue, greenish blue, very strongly greenish blue, or green-blue, finest color being moderately strong medium-dark blue to slightly greenish blue Maxixe Beryl: dark blue, but the color fades at different rates in the sunlight or heat Morganite (Pink Beryl): pink, rose, peach, and salmon Red Beryl (Bixbite): Rasberry red, purplish red to orange-red hue, generally transparent but can be transculent Yellow/Golden Beryl: rich shades of yellow and gold, sometimes have an orange or greenish tint Green Beryl: very strongly bluish green, bluish green, very slightly bluish green, green, slightly yellowish green, yellowish green, or strongly yellowish green CHEMICAL COMPOSTION: Topaz: allochromatic- colored by trace elements or defects in its crystal structure,Chromium causes natural pink, red, and violet-to-purple colors in topaz, Color centers cause yellow, brown, and blue, when both chromium and color centers are present they create orange, prolonged heat and sun light can cause color fading Aquamarine: Trace element of iron Green Beryl: trace elements of by iron, with perhaps some chromium FORMING SOURCE: Topaz: some grow in metamorphic rocks or in hydrothermal veins but most form in cavities in igneous rocks like granite and pegmatite. Aquamarine: grows in pegmatites, alluvial deposits yield most material Morganite (Pink Beryl): Trace elements of manganese, found in pegmatite Red Beryl: Trace elements of manganese,fissures of rhyolite—a light-colored, finely grained igneous rock Yellow Beryl: Trace elements of iron CRYSTAL STRUCTURE: Topaz: orthorhombic crystal system, typically elongated with strong parallel grooves, or striations, parallel to the length, has basal cleavage issues, Imperial crystals are typically 2,5cm to 20cm in length with 10cm diameter Aquamarine: typically six-sided columns with flat faces at their ends, crystals very small to very large—up to 45 kg (100 lbs), with large sizes being more readily available POSSIBLE PHENOMENA: Aquamarine: Pleochroic, showing near-colorless and strong blue in different crystal directions Morganite (Pink Beryl): distinct pleochroism—pale pink and a deeper violetish pink Red Beryl: pleochroic shades of purplish red to red to orangy red COMMON TREATMENTS: Topaz: heat treatment or a comb of heat and radiation is used to create or change color of many varieties of topaz, heat treatment is done carefully as the topaz is prone to break,cloudying and shattering, yellow to reddish topaz a salmon to purple-red color, highly saturated yellow to reddish brown colors creates pink only when chromium is present, heating is also done to on purplish-to-bluish stone to get pink, coating topaz (besides blue) is marketed with descriptive terms like “mango” and “peach” topaz Blue Topaz: radiation and heat to produce blue hues in topaz, as well as coatings typically on the pavilion (which isn't durable/), heat and chemicals can also create blue topaz Aquamarine: Nearly all the blue is heat treatment of bluish green, greenish yellow, or even brownish yellow gems, the heat removes the yellow leaving the pure blue, greenish blue aquamarine is untreated Maxixe Beryl: irration can bring back the blue if the color is faded Morganite (Pink Beryl): heat and irradiation,heating eliminates the yellow or orange tint Red Beryl: clarity treatments include fill fractures with colorless oils or synthetic resins, not heat treated Yellow Beryl: Irradiated improves the color, heat treatment can turn them an aquamarine color Green Beryl: heat treatment turns green to blue green, and irradiation turns greenish yellow to yellowish green COUNTRIES OF ORIGIN: Topaz: fine Imperial topaz mined in the Ouro Preto area of Minas Gerais in Brazil, red and purple or red and orange are minded in Ouro Preto, red and pink are found in Pakistan—Ghundao Hill, also found in Brazil, Sir Lanka, Australia, Madagascar, Mexico, Myanmar, Namibia, Nigeria, and the US Aquamarine: most import source is Brazil at northeast Minas Gerais, Pakistan is another significant source, Australia, Vietnam, Kenya, Madagascar, Mozambique, Nigeria, the US, and Zambia, China produces most commercial quality Maxixe Beryl: Paiuhy region of Minas Gerais state, Brazil Morganite( Pink Beryl): Minas Gerais, Brazil. Afghanistan, Mozambique, Namibia, and the US have been minor and inconsistent sources Red Beryl: Wah Wah Mountains in the US state of Utah, the mined closed in early 2000's Yellow Beryl: Minas Gerais, Brazil. Other sources are Namibia, Madagascar, and Sri Lanka Green Beryl: Brazil, Zimbabwe, and Australia COMMON CUTS: Topaz: often oval, pears, and emeralds due to elongated crystal structure, often place in protective mounting due to cleavage Aquamarine: emerald cuts or as round or oval brilliants, fancy cuts and ornamental Red Beryl: often cut into melee sizes, average faceted red beryl is 0.15 ct, 1ct is rare, largest cut 8ct Yellow Beryl: typically emerald and placed in rings, brooches, pendants, or earrings CLARIETY CHARACTERISTIC: Aquamarine: most are eye clean, but they can get liquid inclusions Red Beryl: fingerprint and two-phase inclusions, unhealed fractures, solid crystal inclusions, distinct color zoning, and growth features Yellow Beryl: typically eye clean MAIN SYNTHETIC PROCESS: Aquamarine: hydrothermal synthetic from Russia Morganite (Pink Beryl): hydrothermally in Russia COMMON IMITATION MATERIAL: Aquamarine: treated blue topaz, pale blue glass, and synthetic blue spinel colored by cobalt Maxixe Beryl: irradiated aquamarine TRADES NAMES: "Rose Topaz" term used for pink topaz, "Sherry Topaz" orange-to- yellow to brown topaz is sometimes called "precious topaz", “cyclamen pink” a violet-pink topaz from Pakistan Red Beryl: "red emerald", " bixbite" "raspberry red" Yellow/Golden Beryl: "heliodor" CUTTING/TRADING CENTER: Topaz: mined in Brazil is cut in Brazil, Other important cutting centers are in Germany, Thailand, and China Aquamarine: Idar-Oberstein, German Morganite (Pink Beryl): Shenzhen, China, and Jaipur, India