Strictly, gem is the natural nonmetallic mineral monocrystal. It is
extremely hard and resistible to scratching (hardness up to 6 Moh's),
with bright pure color and strong luster, very transparent, and suit
for the craft request. Here the gem we are talking about is the substitute
of natural gem and not really the natural gem, such as cubic zirconia,
synthetic ruby, synthetic sapphire, synthetic spinel, glass and so
on artifical product.
color: Gem is the precious treasure with beautiful color in the
nature.Some gem is pure bright, and some is florid.Its color is
a very important element, and a little change in color can badly
affect its value.So gem's color must be bright like the sun, pure
as a lily, and brilliant like the flash, that tree features are
complements to each other, not a single one can be omitted.Synthetic
gem has many color, such as white, black, light golden, dark golden,
pawpaw yellow, red, pink, tangerine, pomegranate red, mauve, green,
olive, apple green, blue, water blue, change blue, violet, sapphire
and so on.
transparency: Transparency is the degree to which light passes through
a substance. It's one of the most important standards to value gem's
quality. The dark gem is not so transparent as the light or pure
luster: When the light project to the surface of gemstone, some
of them was refracted and assorted, and the other was reflected.
The light reflected forms the gem's luster. Various gems have various
texture, hardness, and the reflectivity and absorption
to light differs from each other, so their luster is different.
That's why the diamond's luster is very bright and amazing when
the emerald's luster is soft. Luster is also is one of the important
standards to value gem.
density: Density is the mass per unit volume of gem. Its unit is
gram/cm3.The table below shows the densities of common gems: