hollow
cone. Double Refraction: In crystals that are not homogeneous but have
different properties of elasticity, etc., in different directions, if a rav °* light enter the crystal in some particular directions it is not simply refracted but divided into two rays.
Rejections. Diamonds not worthy of cutting.
Reniform. Kidney-shaped.
Resinous. The lustre of yellow resins; manifested in the common forms of garnets.
Rhombs. Lozenge-shaped faces.
Rivers. Diamonds found in the beds of rivers.
Röntgen Rays. (See X-rays.)
Rosette. (Rose-cut.)
A form of cutting in which the stone's base is a single face; the
general form is pyramidal and the several varieties each possess a
different number of facets; a Double Rosette, also called " Pendeloque
" is of the form of two rosettes joined at their bases.
Rough. Uncut crystals.
Round-Stones. Diamond crystals with arched facets.
Schist. A
term used for rocks consisting of mineral ingredients arranged so as to
impart a more or less laminar structure that may be broken into slabs
or slaty fragments.
Second Bye. Fifth grade of rough diamonds.
Second Cape. Third grade of South African rough diamonds.
Semitransparent. When objects are visible through a mineral, though the outlines are indistinct.
Sharps. Thin, knife-edge pieces of diamond.
Siams. Dark, garnet-coloured rubies usually f°un" in Siam.
Sight. Exhibition of rough diamonds by the London Syndicate to applicants for the privilege of inspecting and purchasing.
Silk. White, glistening streaks in the grain of rubies.
Silky. A lustre suggesting silk, as exhibited by crocido-lite.
. ,
Silver Capes. Diamonds having a very slight tint ο yellow.
