Emerald And Diamond Sapphire Pendant Set Jewellery Collection 39

Emerald Diamond Sapphire Pendant Set Jewellery. 

Fashion jewellery emerald and diamond sapphire pendant set gold jewelley kohls-sterling-silver-simulated-emerald-labcreated-white-sapphire-pendant-ring-stud-earring-set

 By Aamir Mannan.

15.-3 REFRACTIVE INDEX AND ITS MEASUREMENT

The totally and the only partially reflected rays are projected by a lens system on to a transparent scale which is viewed through an eyepiece. the part of the scale illuminated by the totally reflected rays will be brightly lit, while the rest of the scale will be relatively in shadow. the scale is calibrated by the marks of the instrument so as to read direct in refractive indices, so that by simply observing the positions of the edge of the shadow on the scale the refractive 

index of the stone tested can be ascertained. Refractometer of the total reflection type were in use during the latter half of last century, but the first satisfactory low priced instrument for testing precious stones was devised by Dr. G. F. Herbert Smith in 1907. the more recently designed and very compact rayner refractometer figure 2.3 (a) has a truncated prism of dense glass in place of the usual hemisphere, but the principle of the instrument is exactly the same. the prism form was originally evolved to allow isotropic minerals to be use in glass. special anderson-payne models incorporating synthetic spinal, blend, and diamond have been made which have certain advantages as well as certain limitations compared with

Emerald And Diamond Sapphire Bracelet Jewellery Collection 38

Emerald Diamond Sapphire Bracelet Jewellery

Fashion jewellery emerald and diamond sapphire bracelet 18k gold  sapphire emerald and diamond bracelet

By Aamir mannan.

14.-2 DOUBLE REFRACTION AND DISPERSION

When a doubly refractive stone is too small or has to low a birefringence to show doubling at all easily by the straight forward lens inspections describe above, another simple but more sensitive technique may yield valuable information. this has been practised indipendently in the past by max bauer, G.O. Wild, G.O. crowning shield and R.K. 

Mitchell, and in recent years has been systematiesd into a routine process of visual optics by alan hodgkinson, who uses it with exceptional skill and success.  The method is best applied in a darkened room with a single light source, which may be either a clear electric bulb with 'C' filament or (more conveniently) a small 'slit' torch of the type produced by hanneman lapidary specialist (figure 3.2). the stone to be examined, if large or

Emerald Sapphire Diamond Earrings Jewellery Collection 37

Emerald Sapphire Diamond Earring Jewellery.

Fashion jewellery platinum diamond emerald sapphire earrings gold and white  Jewellery.

 By Aamir Mannan. 

13-1.REFRACTIVE INDEX AND ITS MEASUREMENT

There is a point here which may usefully cleared up since it causes confusion to students. what is known as the critical angle of a stone is the angle at which rays of light passing from the stone into air are refracted at 90 to a line prependicular to the surface between the two media . rays striking the inside surface of a stone at angle creater than this critical angle cannot emerge, and are totally reflected back into the stone. here the stone 

is the denser medium, and the higher the refractive index of the stone is the smaller is its critical angle. in the case of refractomemter the principle is exactly the same, but here the glass of the refractometer is the denser medium, and the stone is the rarer medium. thus, in this case the higher the refractive index of the stone the greater is the critical angle between it and the glass of the instrument.

Emerald Sapphire And Diamond Ring Jewellery Collection 56

Emerald Sapphire Diamond Ring Jewellery.

 Fashion jewellery platinum old mine diamond emerald sapphire ring 18k gold jewellery
By Aamir Mannan.

12.-3 COLOUR, COLOUR FILTERS, AND THE DICHROSCOPE

When even the most practised eye may find it difficult to distinguish between stone of difficult species but of very similar colour, simple instruments can sometimes be used to 'analyes' the colour in one way or another and make the separation simple. what we call 'white' light, i.e. light from the sun or other incandescent bodies, is composed of a mixture of all the colours of the rainbow. newton, in the year of the great fire of london (1666), was the first 

to show that sunlight has a composite nature. he analysed a narrow beam of light that passed through a chink in the shutter into his darkened room, by the simple expedient of placing a glass prism in the path of the ray. light is variously refracted by a transparent solid according to its wavelenght, the red rays, of longer wavelength, beings less deviated than the shorter, violet, waves.

Emerald Beautiful Nose Pin Jewellery Collection 36

Emerald Beautiful Nose Pin Jewellery.

Fashion Jewellery by emerald nose pin new item emerald nose stud set in sterling silver and gold  l screw or bone nose pin

 By Aamir Mannan. 

11-2.DOUBLE REFRACTION AND DISPERSION

As With any other test, practice and perseverance are needed, and when the beginner has become accustomed to getting results in easy specimens he should strive to develop his skill to the limit and learn to gauge approximately the strength of the double refraction shown. the author has found this to be a most valuable accomplishment. the more thing that can be learned with a pocket lens the better-even if one possessed other apparatus this will not usually be available in an auction room or on other people's premises. this same test can, of course, be extended and rendered easier b using a microscope, which functions as a much more powerful lens, magnifications of 25 to 60 diameters being quite comfortable usable with stone held between the thumb and forefinger of the left hand,

Emerald And Crystal Ankle Bracelet Jewellery Collection 35

Emerald And Crystal Ankle Bracelet Jewellery.

Fashion Jewellery by gold and crystal anklet emerald green swarovski and gold ankle bracelet 

By Aamir Mannan. 

10-1.REFRACTIVE INDEX AND ITS MEASUREMENT

If therefor in any two media which are in optical contact we can measure the angle where total reflection beings (i.e. the critical angle), and we known the refractive index of the denser medium. it is possible to calculate the refractive index of the rarer medium. this is the 

underlying principle of all total reflection refractometers (sometimes called total refractometers), but in the instruments designed for gem testing all calculation is ingeniously avoided. In such refractometer the optically dense medium of known refractive index is in the form of polished hemisphere of heavy lead glass, or a segment of such a hemisphere, or a truncated 60o prism of the same material, the flat upper surface in each case forming the 'table' of the instrument. if the flat, polished surface of any gemstones of

Emerald And Laois Lazuli Bracelet Jewellery Collection 34

Emerald And Laois Lazuli Bracelet Jewellery.

a Fashion jewellery by lapis lazuli and emerald chrysoprase and 18k gold bracelet 

By Aamir mannan.

9-3.COLOUR, COLOUR FILTERS, AND THE DICHROSCOPE

It is the presence of traces of these in an otherwise colourless crystal that produces their colour varieties. more will be said about the function of these 'transition' element , when dealing with the spectroscope. granted that there are a considerable number of red, 

blue and green gemstones, there are very few that can approach ruby, sapphire and emerald in their rich shades of these colour and a colour sensitive and trained eye can go a long way towards distinguishing them from other natural gemstones, glass imitations, or even synthetic counterparts. it is indeed worthwhile for a beginning gemmologist to practice at every opportunity the sight identifications of the various gems and to pay special attention to the particular grades of colour typical of each species.

Emerald And Ruby Locket Jewellery Collection 33

Emerald And Ruby Locket Jewellery. 

Fashion jewellery collection emerald and ruby pendnit set  locket set emerald jewellery.

 (By Aamir Mannan) 

 COLOUR, COLOUR FILTERS, AND THE DICHROSCOPE

While ruby and supphire are the red and blue varieties of the mineral corundum, there are also white, yellow, pink and green supphires. emerald and aquamarine are the rich green and pale blue varieties of beryls, but there are also white, pink, and yellow beryls, and green beryl that do not rank as emeralds, tourmaline, quartz, zircon and topaz are further well-

known examples of such polychrome minerals, and tourmaline in particular is well known for frequently appearing as parti-coloured crystals, the boundaries between the colours -(usually green and

Emerald And ruby Bridal Pakistani Jewellery Collection 32

Emerald And ruby Bridal Pakistani Jewellery.

Fashion jewellery in emerald and ruby bridal weddings jewellery iijw-13-grand-finale-gold-ruby-briolette-earrings-necklace.

By Aamir Mannan.

DOUBLE REFRACTION AND DISPERSION

As would appear in a singly refractive stone such as diamond, each edge appears as a double line (see figure 3.1). a word of warning, however, should be uttered here; according to their crystal structure, all doubly refracting stones have either one or two direction in which only single refraction obtains. those gemstones belonging to the tetragonal, 

trigonal or hexagonal system of crystals have only such direction; one 'optic axis' as it called. these minerals, which are grouped together optically us 'uniaxal', include zircon, corundum (ruby and sapphire), beryl (emerald and aquamarine), tourmaline, and quartz (amethyst and citrine). the minerals crystallising in either the orthorhombic, monoclinic or triclinic systems have two optic axes, and are called 'biaxial'. these include peridot, chrysoberal (alexandrite), topaz, and spodumene (kunzite) among the coommoner gemstones.

Emerald Ruby Earrings Jewellery Collection 30

Emerald Ruby Earrings Jewellery. 
Fashion Jewellery kundan-emerald-and-ruby-dangler-earrings 18kgold earring jewellery collection
By Aamir Mannan.
COLOUR, COLOUR FILTERS, AND THE DICHROSCOPE

Colours plays an extermely important part in contributing to the beauty and popularity of precious stones. it was their colour that made such stones as turquoise and lapis lazuli among the first to attract the cupidity of early civilised man, and it is the mangnificent crimson red of ruby, the deep cornflower blue of the finest sapphires and the verdant green of emerald which (added to their transparency, hardness and rarity) have caused them always to rank amongst the supremely precious gems. only in the case of diamond, 

unique in this as in so many other ways, has a complete lack of colour been  regarded as the standard of perfection. those unversed in gemmology find it hard to realise that is most of the mineral species used as gems a wide colour range is possible, and that in their 'pure' state they would be colourless and thereby of relatively little value.

Emerald And Ruby Beautiful Rings Jewellery Collection 31

Emerald And Ruby Beautiful Rings Jewellery.

Fashion jewellery vintage-butterfly-diamond-ruby-sapphire-emerald-wedding and party ring-14k-gold jewellery.

 By Aamir Mannan 

REFRACTIVE INDEX AND ITS MEASUREMENT

It has already been stated that each mineral has a definite refractive index by which it can be identified on the refractometer; list of these indices will be found on p. 27, and at the of the post. for the benefit of those who like to have at least a rough idea of the working of an instrument which they are using, a short description of the basic principle upon which all gem-tasting 

refractometer depend followers. however, those, who would like to know how to use a refractometer, but who prefer to shirk such explanation, can skip the next section and await the strictly practical directions which will be given later, on p.21. what followers can best be understood by considering the diagram, figure 2.2. here rays of light are considered passing from a dense medium into a rarer one, say from glass into air. the rays will

Emerald And Ruby Bridal Jewellery Collection 29

Emerald And Ruby Bridal Jewellery. 
EMERALD-RUBY AND DIAMOND-DEUX-FLEURS-CLIP-BROOCH-AND NECKLACE SET BRIDAL AND FASHION JEWELLERY
 BY AAMIR MANNAN. 
DOUBLE REFRACTION AND DISPERSION

In some minerals the figures very somewhat; thus in zircon, while the blue, white, and golden 'fried' type most popular in moderan jewellery are almost constant in their birefringence of 0.059. many of the ceyclonese zircons. particularly the green varieties, have a much lower double refractions, sinking in some cases practically to zero. this peculiaity is unique amongst minerals, and will be discussed at greater length in the chapter on zircon. 

synthetic rutile has been manufactured in the USA (since 1949), and its anormous double refraction will be one means of identification. calcite, though not a gemstone, plays an important part in gemmological instruments in its optocally pure form of 'ice land spar', how, apart from the refractometer, can one test whether a given stone doubly refractive or not? the simplest method of all, which with a little practice is quite easily carried out, is to examine the stone carefully with a powerful pocket lens-say giving 8x to 12x magnification. for example, look

Emerald And Pearl Jewellery Collection 28

Emerald And Pearl Jewellery.
Fashion jewellery an_emerald_and_cultured_pearl_necklace_set and gold emerald and pearl jewellery by_fashion jewellery 

Aamir mannan. 

REFRACTIVE INDEX AND ITS MEASUREMENT

This deviation of rays of light on entering a new medium is called refraction. In figure 2.1 the rays of light, I.O, is refracted along OR  on entering the denser medium blow the surface PQ. The broken line show the path of  followed by the reflacted light. The 

extent of the bending of refraction of light on entering the stone depends upon its refracting power or 'refractive index', and this is inversely proportional to the velocity of light withing the substance. Put differently, the refractive index of a medium may be define as the velocity of light in air* divided by the velocity of light in the medium. The velocity of light in air approximately I86,000 miles per second, and light from the sun and stars travel to us at this immense speed. In quartz (rock, crystal, amethyst, etc) the velocity is reduced to approximately I20,000 and its diamond to only 76,860 miles per second. Thus diamond, in which light travels as mentioned above, at 76,860 miles per second in empty space, has a refractive index of I86,000\76,860=2.042; higher then the refractive index of any other gemstones used in

Emerald And Pearl Necklace Set Jewellery Collection 27

Emerald And Pearl Necklace Set Jewellery.

By Fashion Jewellery.emerald-And pearl influenced-style-indian-and uk pearl-belt-necklace-converter-chain-jewelry-versatile-spring-2013celebrity-designer-trends jewellery.        By Aamir mannan.

 Refractive Index And Its Measurement. How To  Use The Refractometer. Though refractometers are essentially very simple to use, the beginner will do well to read carefully the instructions and warnings thats follow most of which will apply to any present day types of jewellers refractometers. remember above all that the sureface of the prism on which the stone is placed consists of a very soft form of glass and is therefore easily scractched by a corner or edge of the stone that are being 


tested good reading can only be expected if the surface is preserved in an unblemished state. the standard type of refractometer will be dealt with first. the instrument should be placed on a steady bench or table, and should be mounted on some stand or block to allow for easy reading a bench lamp or adjustable reading lamp fitted with a 60 watt pearl blub provides adequate illuminations and should be so arranged that the light can pass direct from the lamp to the window

Emerald and Pearl Earrings Jewellery collection 26

Emerald and Pearl Earrings Jewellery.
Fashion jewellery.Antique-Style-Gold-Kundan-Pearl-Emerald-and diamond-Dangle-Earring jewellery
By Aamir Mannan.
16.REFRACTIVE INDEX AND ITS MEASUREMENT
(The Dialdex Refractometer)

In 1972 Rayner succeeded in producing a refractometer of quite a new type although it acts upon the same principles as all others. in place of the customary scale of the conventional refractometer, the user (having placed the usual small drop of contact liquid and the stone to be tested on the table of the instrument) sees through the eyepiece a blank 

screen crossed with the faint shadow edge or shadow edge due to the stone. the position of which will depend, as usual, on the refractive index or indices of the stone. by the turning the calibrated dial at the side of the instrument a black ribbon-like marker can be adjusted to coincide with each shadow-edge. the corresponding refractive index can than be read very easily from the dial hence the name 'dialdex'. reading accurate to one or two units in the third decimals place can be assured on this instrument rather more

Emerald And Pearl Beautiful Ring Jewellery Collection 25

Emerald-and-Pearl-Beautiful-Ring.

Fashion jewellery By Aamir Mannan-18-Karat-Gold-Emerald-and-Pearl-Beautiful-Ring-Last-Quarter-19th-Century of world.

The totally and the only partially reflected rays are projected by a lens system on to a transparent scale which is viewed through an eyepiece. the part of the scale illuminated by 

the totally reflected rays will be brightly lit, while the rest of the scale will be relatively in shadow. the scale is calibrated by the marks of the instrument so as to read direct in refractive indices, so that by simply observing the positions of the edge of the shadow on the scale the refractive index of the stone tested can be ascertained. Refractometer of the total reflection type were in use during the latter half of last century, but 

the first satisfactory low priced instrument for testing precious stones was devised by Dr. G. F. Herbert Smith in 1907. the more recently designed and very compact rayner refractometer figure 2.3 (a) has a truncated prism of dense glass in place of the usual hemisphere, but the principle of the instrument is exactly the same. the prism form was originally evolved to allow isotropic minerals to be use in glass. special anderson-payne models incorporating synthetic spinal,

Emerald Diamond Party Earrings Jewellery Collection 24

Emerald Diamond Earrings Jewellery.
By Aamir Mannan.
16. DOUBLE REFRACTION AND DISPERSION

hemisphere, but the principle of the instrument is exactly the same. the prism form was originally evolved to allow isotropic minerals to be use in glass. special anderson-payne models incorporating synthetic spinal, blend, and diamond have been made which have 

certain advantages as well as certain limitations compared with standard refractometers. in rayne refractometers the scale extends from 1.30 to 1.86. in spinal model the shorter range of 1.30 to 1.68 allows a more open scale to be used, while the long upward range of the diamond refractometer, 1.55 to 2.05, necessitates a sliding eyepiece for scanning the scale. Several refractometer to Amarican manufacture are available in the U.S.A these operate on precisely the same principle as the british

Emerald Diamond Bridal Bracelet Jewellery Collection 23

Emerald Diamond Bridal Bracelet Jewellery.
By Farzana Aamir.
15.REFRACTIVE INDEX AND ITS MEASUREMENT

The totally and the only partially reflected rays are projected by a lens system on to a transparent scale which is viewed through an eyepiece. the part of the scale illuminated by the totally reflected rays will be brightly lit, while the rest of the scale will be relatively in shadow. the scale is calibrated by the marks of the instrument so as to read direct in refractive indices, so that by simply observing the positions of the edge of the shadow on the scale the refractive index of the stone tested can be ascertained. 

Refractometer of the total reflection type were in use during the latter half of last century, but the first satisfactory low priced instrument for testing precious stones was devised by Dr. G. F. Herbert Smith in 1907. the more recently designed and very compact rayner refractometer figure 2.3 (a) has a truncated prism of dense glass in place of the usual. 

Emerald Diamond Engagement Ring Jewellery collection 22

Emerald Diamond Engagement Ring.
By Aamir Mannan.
14.DOUBLE REFRACTION AND DISPERSION

When a doubly refractive stone is too small or has to low a birefringence to show doubling at all easily by the straight forward lens inspections describe above, another simple but more sensitive technique may yield valuable information. this has been practised 

indipendently in the past by max bauer, G.O. Wild, G.O. crowning shield and R.K. Mitchell, and in recent years has been systematiesd into a routine process of visual optics by alan hodgkinson, who uses it with exceptional skill and success.  The method is best applied in a darkened room with a single light source, which may be either a clear electric bulb with 'C' filament or (more conveniently) a small 'slit' torch of the type produced by hanneman lapidary specialist (figure 3.2). the stone to be examined, if large or mounted with an open baking, can be held in the hand, or if small in tongs.

Emerald Bridal Girls Jewellery Collection 21- 2013

Emerald Bridal Girls Jewellery.

By Aamir Mannan.

There is a point here which may usefully cleared up since it causes confusion to students. what is known as the critical angle of a stone is the angle at which rays of light passing from the stone into air are refracted at 90 to a line prependicular to the surface between the two media . rays striking the inside surface of a stone at angle creater than this critical angle cannot emerge, and are totally reflected back into the stone. here the stone is the denser medium, and the higher the refractive index of the stone is the smaller is its critical angle. in the case of refractomemter the principle is exactly the same, but here the glass of the refractometer is the denser medium, and the stone is the rarer medium. thus, in this case the higher the refractive index of the stone the greater is the critical angle between it an the glass of the instrument.When a doubly refractive stone is too small or has to low a

birefringence to show doubling at all easily by the straight forward lens inspections describe above, another simple but more sensitive technique may yield valuable information. this has been practised indipendently in the past by max bauer, G.O. Wild, G.O. crowning shield and R.K. Mitchell, and in recent years has been systematiesd into a routine process of visual optics by alan hodgkinson, who uses it with exceptional skill and success.  The method is best applied in a darkened room with a single light source, which may be either a clear electric bulb with 'C' filament or (more conveniently) a small 'slit' torch of the type produced by hanneman lapidary specialist (figure 3.2). the stone to be examined, if large or mounted with an open baking, can be held in the hand, or if small in tongs.

Emerald Party Weddings Jewellery Collection 20

Emerald Party Weddings Jewellery.
By Aamir Mannan.
14.DOUBLE REFRACTION AND DISPERSION

When a doubly refractive stone is too small or has to low a birefringence to show doubling at all easily by the straight forward lens inspections describe above, another simple but more sensitive technique may yield valuable information. this has been practised indipendently in the past by max bauer, G.O. Wild, G.O. 

crowning shield and R.K. Mitchell, and in recent years has been systematiesd into a routine process of visual optics by alan hodgkinson, who uses it with exceptional skill and success.  The method is best applied in a darkened room with a single light source, which may be either a clear electric bulb with 'C' filament or (more conveniently) a small 'slit' torch of the type produced by hanneman lapidary specialist (figure 3.2). the stone to be examined,

Emerald Bridal Fashion Beautiful Jewellery Collection 2013 19

Emerald Bridal Fashion Beautiful Jewellery.
By Aamir mannan.
13.REFRACTIVE INDEX AND ITS MEASUREMENT

There is a point here which may usefully cleared up since it causes confusion to students. what is known as the critical angle of a stone is the angle at which rays of light passing from the stone into air are refracted at 90 to a line prependicular to the surface between the two media . rays striking the inside surface of a stone at angle creater than this critical angle cannot emerge, and are totally reflected back into the stone. here the stone is the denser medium, and the higher the refractive index of the stone is the smaller is its critical angle. in the case of refractomemter the principle is exactly the same, but here the glass of the refractometer is the denser medium, and the stone is the rarer medium. thus, in this case the higher the refractive index of the stone the greater is the critical angle between it an the glass of the instrument.

Emerald Gold Bridal Fashion Jewellery Collection 18

Emerald Gold Bridal Fashion Jewellery.
By Samina Aamir

When even the most practised eye may find it difficult to distinguish between stone of difficult species but of very similar colour, simple instruments can sometimes be used to 'analyes' the colour in one way or another and make the separation simple. what we call 'white' light, i.e. light from the sun or other incandescent bodies, is composed of a mixture of all the colours of the rainbow. newton, in the year of the great fire of london (1666), was 

the first to show that sunlight has a composite nature. he analysed a narrow beam of light that passed through a chink in the shutter into his darkened room, by the simple expedient of placing a glass prism in the path of the ray. light is variously refracted by a transparent solid according to its wavelenght, the red rays, of longer wavelength, beings less deviated than the shorter, violet, waves.There is a point here which may usefully cleared up since it causes confusion to students.

Emerald Fashion Earrings Jewellery collection 17

Emerald Fashion Earrings Jewellery.
By Samina

When even the most practised eye may find it difficult to distinguish between stone of difficult species but of very similar colour, simple instruments can sometimes be used to 'analyes' the colour in one way or another and make the separation simple. what we call 'white' light, i.e. light from the sun or other incandescent bodies, is composed of a mixture of all the colours of the rainbow. newton, in the year of the great fire of london (1666), was the first to show that sunlight has a composite nature. he analysed a narrow beam of light that passed through a 
chink in the shutter into his darkened room, by the simple expedient of placing a glass prism in the path of the ray. light is variously refracted by a transparent solid according to its wavelenght, the red rays, of longer wavelength, beings less deviated than the shorter, violet, waves.There is a point here which may usefully cleared up since it causes confusion to students. what is known as the critical angle of a stone is the angle at which rays of light passing from the stone into air are refracted at 90 to a line prependicular to the surface between the two media . rays striking the inside surface of a stone at angle creater than this critical angle 

Indian Stylish Fashion Jewellery Collection 42

Indian Stylish Fashion Jewellery.
By Fashion jewellery.
13.REFRACTIVE INDEX AND ITS MEASUREMENT

There is a point here which may usefully cleared up since it causes confusion to students. what is known as the critical angle of a stone is the angle at which rays of light passing from the stone into air are refracted at 90 to a line prependicular to the surface between the two media . rays striking the inside surface of a stone at angle creater than this critical angle cannot emerge, and are totally reflected back into the stone. here 

the stone is the denser medium, and the higher the refractive index of the stone is the smaller is its critical angle. in the case of refractomemter the principle is exactly the same, but here the glass of the refractometer is the denser medium, and the stone is the rarer medium. thus, in this case the higher the refractive index of the stone the greater is the critical angle between it an the glass of the instrument.