Opal is a
hydrated amorphous form of silica (SiO2·nH2O); its water content
may range from 3 to 21% by weight, but is usually between 6 and
10%. Because of its amorphous character, it is classed as a
mineraloid, unlike crystalline forms of silica, which are classed
as minerals. The internal structure of precious opal makes it
diffract light. Depending on the conditions in which it formed, it
can take on many colors. Precious opal ranges from clear through
white, gray, red, orange, yellow, green, blue, magenta, rose, pink,
slate, olive, brown, and black. Of these hues, the black opals are
the rarest, whereas white and greens are the most common. Opals
vary in optical density from opaque to semitransparent.
This is a parcel of 5 Authentic Mexican Galaxy Opals ranging from
0.5 to 10 carats each. Each stone is one-of-a-kind from our family
mines in Guadalajara Mexico.