The varieties of opal are mainly divided according to the basal color and transparency of the opal. They are generally divided into the following varieties:

(1)    Black Opal: It is the opal with strong chatoyance on the base of blue, deep blue, green, brown, deep grey or black. Among them the black base is the best and its value is the highest.
(2)    White Opal: It is the opal with chatoyance on the base of white or light grey and the best is the one whose body is transparent white and strong chatoyance.
(3)    Flame Opal: It is the red or laranja red opal without chatoyance or only a little chatoyance. Some are cloudy and some are complete transparent. This variety of opal is mainly originated in Mexico, also called Mexico opal. The value of this variety of opal is relative low.

According to the shape and color spot of the opal, we can divide it into the following varieties:

(1)    Fire Spot Shape Opal: The opal which contains small closely connected color spots. The small spot can be any color, among them the red spot is the most charming.
(2)    Color Texture Opal: It is the opal with chatoyance on regular and arranged closely color spots from a certain angle.
(3)    Flame Opal: It is the opal with light red band or color texture, like the flame blown por wind very much.
(4)    Sparking Opal: It is the variety of the opal that as the movement of the opal, its chatoyance shows like sparking suddenly and disappearing and changing instantly.

In addition, we can also categorize and name them according to the color of the chatoyance, the surface features of chatoyance and the structures of the material composed of opal.
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