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table facet
the largest facet on the crown of a gemstone

teardrop
drop- or pearshaped stone with smooth surface; round or oval cross section

translucent
transmitting some light

trapiche emerald
a special form of emerald; the spanish word "trapiche" denotes the cogwheel with which sugarcane is crushed. in trapiche emerald inclusions of coal-black shale form a pattern resembling the spokes of a wheel. there are at least four types of trapiche emerald:

• a black-bordered core from which black spokes emanate
• a solid black core with black spokes
• coreless with 6 spokes meeting in the center
• core and spokes consisting of emerald with sandstone in between (reverse trapiche)

the phenomenon was also observed in rubies from myanmar (burma) and vietnam

trichroism
tri-colouredness; a form of pleochroism

trilliant cut
also trillion, a triangular cut with outwardly curved sides. has more or less replaced the classic straight-sided triangel as trilliants are much less susceptible to damage during cutting and setting.

triplet
a composite stone consisting of three parts. most common in opal when a paper-thin layer of opal is glued onto a base of onyx or plastic and covered with a glass- or sometimes rock crystal top

tumbled
cheap gemstones are not polished by hand individually, they are tumble-polished in large quantities in rotating or vibrating tumbling machines which results in irregularly shaped "pebbles".

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