According to Mr.Birch, it is, generally speaking, "finer in its paste, brighter in its color, employed in thinner masses, and for purposes not known in Egypt." Abundant and excellent clay is furnished by the valley of the Tigris, more especially by those parts of it which are subject to the annual inundation.

The chief employment of this material by the Assyrians was for bricks, which were either simply dried in the sun, or exposed to the action of fire in a kiln.

In this latter case they seem to have been uniformly slack-baked; they are light for their size, and are of a pale-red color.
The clay of which the bricks were composed was mixed with stubble or vegetable fibre, for the purpose of holding it together--a practice common to the Assyrians with the Egyptians and the Babylonians.

This fibre still appears in the sun-dried bricks, but has been destroyed by the heat of the kiln in the case of the baked bricks, leaving behind it, however, in the clay traces of the stalks or stems.

The size and shape of the bricks vary.