SUBJECT: unknown rock formation

I have obtained a sample of rock formation that I was told came
from Saudi desert area.  It may  be described as follows:  several
layers of what appears to be crystallized sand in the shape of a disk,
each disk 3 to 4 inches in diameter. Approximately ten to twelve disks
are fused together to form a series of overlapping disks.  On the top or
outermost disk, partial disks were being formed perpendicular to the
other disks. I have been told that this formation was referred to as a
desert diamond?
I would like to know what these formations are called and how
they were formed and if they can be found in other deserts in other
parts of the world?
Thank you for any help on this matter.
Robert Burge
Rburge@mail.dot.state.de.us