Oolite

Oolite was a variety of quartz which occurred in tiny egg-shaped spherules.

Description
These ornamental stones were usually solid brown in color and was very similar to algae. Individual oolite spherules were about one sixteenth of an inch (one to two millimeters) which was too small to be cut. The aggregate stone was usually polished to bring out the color and mounted in silver jewelry (particularly tiaras or pectorals). A typical stone had a base value of 10 gp.