ULTRASONIC CLEANER A machine that cleans
jewelry by using a fluid that
is vibrated at 20,000 cycles
per second. When the vibration
speed rises above the ultrasonic
frequency level, bubbles explode
and generate strong power,
cleaning the surfaces and
cavities of hard-to-clean
objects. Ultrasonic cleaning
does not scratch the surface
or harm objects like many
chemical or abrasive cleansers.
UNAKITE
Unakite is an opaque mineral
that is green with patches
of red and pink. Unakite is
a variety of granite that
contains green epidote and
pink feldspar (but lacks mica).
It has a hardness of 6 to
7 and a specific gravity of
2.86 - 3.2. Unakite was named
for the Unaka Mountains Mountains
in Tennessee, USA. Unakite
is found in the USA and Africa.
UREA BAKELITE Urea bakelite is
a type of thermoset plastic.
UVAROVITE An emerald green
garnet composed of chromium
lime. Named from the Russian
Count Uvaroff. Uvarovite is
almost never used as a gemstone.
Distinguishing Uvarovite and
Tsavorite is difficult, but
an experienced gemologist
can do it.