singly refractive Diamond is singly refractive since the light traveling through it has a consistent refractive index regardless of the direction it enters.
In singly refractive (SR) gems, light which enters remains as non-polarized beams, and travels through all crystal directions at the same speed. There is one refractive index (RI), no birefringence and no pleochroism.
singly refractive
diamond, garnet, spinel
Tetragonal systems
3 crystallographic axes at right angles to each other - two of equal length, one longer or shorter ...
Being singly refractive, the opposite of doubly refractive (bi-refringent or anisotropic). Diamond is normally isotropic, but can be bi-refringent because of inclusions or internal strain.
Israel ...
The RI of singly refractive (isotropic) and doubly refractive (anisotropic) can also be determined. Refractometers can also be used to distinguish anisotropic optically uniaxial and biaxial gemstones and photopositive or photonegative gemstones.
Optics -- Singly refractive. R.I. about 1.54. Typically displays internal stress patterns under a polariscope.
Durability -- very soft, hardness about 2 to 2.5.
Crystal structure -- amorphous.
Some gemstones are singly refractive. They exhibit only one colour to observer. There are also gemstones which exhibit two different colours of light.
If the material is singly refractive (as in the case of diamond, garnet, spinel, and glass), single images of each of the reflecting facets will appear on the card, but if doubly refracting--even if slightly so--double images will appear.
Diamond: A mineral composed essentially of carbon that crystallizes in the 'cubic,' or 'isometric,' crystal system and is therefore singly refractive.
Birefringence Some gemstones are singly refractive: they have only one refractive index. Other gemstones (in fact, most) are doubly refractive: they have two different refractive indices.
Under polarized light singly refractive substances do not change in brightness when the stone is rotated around 360°; a doubly refractive stone will become lighter four times when rotated around a full circle.
Single Refraction Diamond is normally singly refractive, many gemstones are doubly refractive (bi-refringent), and diamonds can also be doubly refractive because of internal strain or inclusions.
Today, spinels can be easily identified by their refractivity. Since red spinels are singly refractive and rubies doubly refractive, the primary color in red spinels appears purer and more intense than the reds seen in many rubies.
OPTIC CHARACTER: The nature of a gem as either uniaxial (singly refractive) or biaxial (doubly refractive).
ORIENT: The iridescent luster of a pearl.
Fusion causes the loss of its crystalline structure to become singly refractive beryl glass. Simon & Schuster's Guide to Gems and Precious Stones states that "morganite is not as a rule imitated, nor is it produced synthetically.
All the members of the commission and the owner of the stone have viewed the two images. It is without question neither a diamond or another singly refractive stone.
It is composed of three axes of equal length that intersect each other at 90° angles. It is commonly called the cubic system. All gemstones in this category are singly refractive. Examples include diamond, spinel and garnet.
and this is known as s substances Refractive Index (RI). Some substances can split light into two beams and are known as doubly refractive (DR) and will have two Refractive Indexes. If the light beam does not split a substance is Singly refractive ...
(1.62); blue glass is, of course, singly refractive and not dichroic. Although laboratory (hydrothermal) synthesis of aquamarine has been achieved, synthetic aqua is not yet (c.1998) widely available.
 See also: Stone, Gemstones, Gemstone, Crystal, Color
  
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