The most usual colors are blue, yellow, and white; brown, purple, and lilac have been met with occasionally.

These colors are thought to be derived chiefly from metallic oxides, over which was laid as a glazing a vitreous silicated substance.

On the whole, porcelain of this fine kind is rare in the Assyrian remains, and must be regarded as a material that was precious and used by few.
[Illustration: PLATE 83] Assyrian glass is among the most beautiful of the objects which have been exhumed.

M.Botta compared it to certain fabrics of Venice and Bohemia, into which a number sit different colors are artificially introduced.

But a careful analysis has shown that the lovely prismatic hues which delight us in the Assyrian specimens, varying under different lights with all the delicacy and brilliancy of the opal, are due, not to art, but to the wonder-working hand of time, which, as it destroys the fabric, compassionately invests it with additional grace and beauty.
Assyrian glass was either transparent or stained with a single uniform color.