Agate is a cryptocrystalline variety of silica, chiefly chalcedony, characterized by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks.
Lapis is a deep blue semi-precious stone prized since antiquity for its intense color. The intense blue color is due to the presence of the trisulfur (S3) radical anion in the crystal. Lapis lazuli is a rock whose most important mineral component is lazurite. Most lapis lazuli also contains calcite (white), sodalite (blue), and pyrite (metallic yellow). Lapis takes an excellent polish and can be made into jewelry, carvings, boxes, mosaics, ornaments, small statues, and vases.