Gemology

Written by Alain Darbellay GGGems


Continued from page 1
other things of methylene iodide which shows an index of refraction of 1.81 (this liquid is toxic) Dichroscope of whichrepparttar principal part is made up of a tube comprising a window withrepparttar 109303 one ofrepparttar 109304 ends and a lens withrepparttar 109305 other, betweenrepparttar 109306 two is assembled a piece of calcite, chosen because of its strong double refraction so that two images ofrepparttar 109307 window appear side by side torepparttar 109308 observer which looks inrepparttar 109309 eye-glass. The light ofrepparttar 109310 adjacent images ofrepparttar 109311 window vibrates in two perpendicular plans one torepparttar 109312 other at a rate of one only plan for each image. The rotation ofrepparttar 109313 stone is a significant factor duringrepparttar 109314 control of dichroism, bus in allrepparttar 109315 double refraction stones, it exists one or two directions of unirefringence, known as optical axe. The Chelsea color filter. There is a very effective means to reveal repparttar 109316 subjacent differences in color, it isrepparttar 109317 use of colored filters. They are especially effective inrepparttar 109318 differentiation of natural and synthetic emerald. The optical fiber lamp is useful to distinguish inclusions in rough stones. Microscopes:repparttar 109319 binocular one, i.e. to double objective is best adapted for gemology. The microscope is of first importance in repparttar 109320 detection of counterfeits. Indeed,repparttar 109321 study of inclusions whichrepparttar 109322 stone can contain is a practical means to identifyrepparttar 109323 gems while explaining to a certain extentrepparttar 109324 conditions under which they were formed in nature. The spectroscope concerns an extremely simple method which allow repparttar 109325 identification of allrepparttar 109326 stones; rough or polished not being able to be seen withrepparttar 109327 refractometer and which even makes it possible to distinguish certain synthetic or glasses. This method makes it possible to analyzerepparttar 109328 nature ofrepparttar 109329 dye ofrepparttar 109330 stone. The way in whichrepparttar 109331 spectroscope analyzesrepparttar 109332 various wavelengths ofrepparttar 109333 light is in theory very simple; that depends onrepparttar 109334 different degree of refraction to which its subjected various rays of each color (wavelength) when they are propagated through a prism of glass or another transparent substance. After having passed through a prism, a narrow parallel beam of white light is spread out in a ribbon withrepparttar 109335 colors ofrepparttar 109336 rainbow,repparttar 109337 visible spectrum. Let us note that a powerful instrument used in many fields of science is at disposal ofrepparttar 109338 gemologists, it isrepparttar 109339 microscope of Raman which spectroscopy supplementsrepparttar 109340 traditional technology ofrepparttar 109341 laboratory. This instrument can give information on samples lower than 1m what is not accessible to any technique. The use ofrepparttar 109342 Raman spectroscopy by imagery is single in order to determine in a nondestructive wayrepparttar 109343 molecular composition of inclusions present inrepparttar 109344 gems. Analyze by fluorescence: four kinds of radiation are used. The first consists simply in passing a powerful luminous ray of a lamp of projection of 500W through a balloon filled with a strong copper sulfate solution, this last absorbs allrepparttar 109345 red light, orange and yellow andrepparttar 109346 filter rays are invisible if one observes through a good red or orange filter. If a substance only lit byrepparttar 109347 beam of blue light in which it is shines while being observed through one of these filters, it emits a fluorescence. The second method of stimulation of fluorescence isrepparttar 109348 used, it uses a lamp with high pressure out of quartz, and whose light is filtered throughrepparttar 109349 glass of Wood.

The third usesrepparttar 109350 ultraviolet radiations of short radiation emitted by a quartz-mercury lamp with low pressure, in whichrepparttar 109351 mercury line with 2537 is dominating.

X-rays representrepparttar 109352 fourth source of radiation, they are dangerous unlessrepparttar 109353 source is not seriously armored. The unit weight and its measurement. It frequently occurs that only an approximate value of repparttar 109354 density of a stone is necessary to differentiate between gems from similar appearance; in this case a control fromrepparttar 109355 density can be carried out by means of liquors of density. The principle of repparttar 109356 method is simple. A stone will be inserted in a less dense liquid, will float in a denser fluid and will remains in suspension in a liquid of equal density. The three liquids are: The bromoforme density 2,9. The methylene iodide density 3,33. The liquor of Clerici density 4,15. PRINCIPAL COLORING ELEMENTS IN THE GEMS. Chromium Ruby, Emerald, Pyrope garnet, grossularite and uvarovite, Tourmaline. Copper Dioptase, Malachite, Azurite. Iron Sapphire, Aquamarine, Citrine, Almandin garnet. Manganese Morganite, Pink tourmaline, Spessartite garnet. Nickel Chrysoprase. Titanium Blue Sapphire. Vanadium Green beryl, Blue zosite , Garnet. GGGEMS.COM

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Ilakaka Madagascar ( Sapphire rush )

Written by Alain Darbellay GGGems


Continued from page 1

VOHIMENA VAOVAO, 25 kilometers far from Ilakaka. One of quote headlight ofrepparttar sapphires production. The higher edges ofrepparttar 109302 rivers abound in sapphires, chrysoberyls, etc. Here inrepparttar 109303 area of Vohimena vaovao. The sandstones, fragile, have been knife cut byrepparttar 109304 river. SANDSTONES of ISALO The base ofrepparttar 109305 group of Isalo is entirely continental. Sometimes significant marine incursions and of long duration were introduced intorepparttar 109306 medium and higher parts. The group of Isalo begins atrepparttar 109307 top from lower Triassic and continues untilrepparttar 109308 end ofrepparttar 109309 Jurassic means. One separates there: Isalo I, atrepparttar 109310 base, especially sandy, continental. Isalo II, argilo - sandy with some marine intercalations. Isalo III, argilo - sandy with side passage to great marine formations. The essential characteristic ofrepparttar 109311 Isalo formations is their main constitution of soft sandstones, very permeable, badly cemented which disaggregate easily on surfaces by giving thick siliceous sand coverings. The porous nature ofrepparttar 109312 sandstones constitutes an excellent tank which storesrepparttar 109313 water ofrepparttar 109314 rains to restore it duringrepparttar 109315 dry season. Sakalama, 60 kilometers south from Ilakaka. MADAGASCAN CORUNDUMS Atrepparttar 109316 back, ruiniform sandstones ofrepparttar 109317 Isalo range. GGGEMS.COM

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