Great care is required in the selection of clays to be used for making agatewares.

在选择用于制作玛瑙器皿的粘土时，需要格外小心。

This will occur both in sands and clays.

这在砂土地和粘土地带常常发生。

Thus clays and shales tend to be impermeable.

因此粘土和页岩就往往不透水。

Thus clays and shales tend to be impermeable .

因此粘土和页岩就往往不透水。

There are, of course, many silty clays and clayey silts.

当然了，你知道，这里面有非常多的粉质黏土和粘质粉。