Antique Roman Agate intaglio. An intaglio is a small gemstone, usually semi-precious, that has been carved with images or inscriptions only on one face, leaving a hollow impression in the untouched background. This style of carving is the opposite of the cameo technique. The engraving of gemstones was a major luxury art form in the ancient world and an important one in some later periods. This particular one is agate and dates from the third century AD and shows a minutely carved lizard. It is in very nice original condition and would be ideal for making into a ring.