Form of Quartz is a term used to describe four different types of quartz, which are AGATE (5 letters), ONYX (4 letters), JASPER (6 letters) and Sard (4 letters). AGATE is a banded variety of quartz that is often used for jewelry and decorative items. ONYX is a black or dark-colored variety of quartz that is often used for jewelry and decorative items. JASPER is an opaque variety of quartz that is usually red, yellow or brown in color and is often used for jewelry and decorative items. Sard is a reddish-brown variety of quartz that is often used for jewelry and decorative items.