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.