Engraved gem
An engraved gem, frequently referred to as an intaglio, is a small and usually semi-precious gemstone that has been carved, in the Western tradition normally with images or inscriptions only on one face. The engraving of gemstones was a major luxury art form in the ancient world, and an important one in some later periods.
Strictly speaking, engraving means carving in intaglio, but relief carvings are also covered by the term. This article uses cameo in its strict sense, to denote a carving exploiting layers of differently coloured stone. The activity is also called gem carving and the artists gem-cutters. References to antique gems and intaglios in a jewellery context will almost always mean carved gems; when referring to monumental sculpture, the term counter-relief, meaning the same as intaglio, is more likely to be used. Vessels like the Cup of the Ptolemies and heads or figures carved in the round are also known as hardstone carvings.
Glyptics or glyptic art covers the field of small carved stones, including cylinder seals and inscriptions, especially in an archaeological context. Though they were keenly collected in antiquity, most carved gems originally functioned as seals, often mounted in a ring; intaglio designs register most clearly when viewed by the recipient of a letter as an impression in hardened wax. A finely carved seal was practical, as it made forgery more difficult – the distinctive personal signature did not really exist in antiquity.
Technique
Gems were mostly cut by using abrasive powder from harder stones in conjunction with a hand-drill, probably often set in a lathe. Emery has been mined for abrasive powder on Naxos since antiquity. Some early types of seal were cut by hand, rather than a drill, which does not allow fine detail. There is no evidence that magnifying lenses were used by gem cutters in antiquity. A medieval guide to gem-carving techniques survives from Theophilus Presbyter. Byzantine cutters used a flat-edged wheel on a drill for intaglio work, while Carolingian ones used round-tipped drills; it is unclear where they learnt this technique from. In intaglio gems at least, the recessed cut surface is usually very well preserved, and microscopic examination is revealing of the technique used. The colour of several gemstones can be enhanced by a number of artificial methods, using heat, sugar and dyes. Many of these can be shown to have been used since antiquity – since the 7th millennium BC in the case of heating.History
The technique has an ancient tradition in the Near East, and is represented in all or most early cultures from the area, and the Indus Valley civilization. The cylinder seal, whose design appears only when it is rolled over damp clay, from which the flat ring type developed, was the usual form in Mesopotamia, Assyria and other cultures, and spread to the Aegean and Minoan world, including parts of Greece and Cyprus. These were made in various types of stone, not all hardstone, and gold rings were a related development in Minoan seals, which are often very fine. The Greek tradition emerged in Ancient Greek art under Minoan influence on mainland Helladic culture, and reached an apogee of subtlety and refinement in the Hellenistic period. Pre-Hellenic Ancient Egyptian seals tend to have inscriptions in hieroglyphs rather than images. The biblical Book of Exodus describes the form of the hoshen, a ceremonial breastplate worn by the high priest, bearing twelve gems engraved with the names of the Twelve tribes of Israel.Round or oval Greek gems are found from the 8th and 7th centuries BC, usually with animals in energetic geometric poses, often with a border marked by dots or a rim. Early examples are mostly in softer stones. Gems of the 6th century are more often oval, with a scarab back, and human or divine figures as well as animals; the scarab form was apparently adopted from Phoenicia. The forms are sophisticated for the period, despite the usually small size of the gems. In the 5th century gems became somewhat larger, but still only 2-3 centimetres tall. Despite this, very fine detail is shown, including the eyelashes on one male head, perhaps a portrait. Four gems signed by Dexamenos of Chios are the finest of the period, two showing herons.
File:Scarab satyr BM Gem 465.jpg|thumb|Reclining satyr, Etruscan, 2.2 cm wide, agate. Note the vase shown "sideways"; it is characteristic of early gems that not all elements in the design are read from the same direction of view.
Relief carving became common in 5th century BC Greece, and gradually most of the spectacular carved gems in the Western tradition were in relief, although the Sassanian and other traditions remained faithful to the intaglio form. Generally a relief image is more impressive than an intaglio one; in the earlier form the recipient of a document saw this in the impressed sealing wax, while in the later reliefs it was the owner of the seal who kept it for himself, probably marking the emergence of gems meant to be collected or worn as jewellery pendants in necklaces and the like, rather than used as seals – later ones are sometimes rather large to use to seal letters. However inscriptions are usually still in reverse so they only read correctly on impressions. This aspect also partly explains the collecting of impressions in plaster or wax from gems, which may be easier to appreciate than the original.
The cameo, which is rare in intaglio form, seems to have reached Greece around the 3rd century; the Farnese Tazza is the only major surviving Hellenistic example, but other glass-paste imitations with portraits suggest that gem-type cameos were made in this period. The conquests of Alexander the Great had opened up new trade routes to the Greek world and increased the range of gemstones available. Roman gems generally continued Hellenistic styles, and can be hard to date, until their quality sharply declines at the end of the 2nd century AD. Philosophers are sometimes shown; Cicero refers to people having portraits of their favourite on their cups and rings. The Romans invented cameo glass, best known from the Portland Vase, as a cheaper material for cameos, and one that allowed consistent and predictable layers on even round objects.
File:Aachen Germany Domschatz Cross-of-Lothair-01.jpg|thumb|There are several antique and medieval engraved gems on the Ottonian Cross of Lothair. Many antique engraved gems survived in such contexts.
During the European Middle Ages antique engraved gems were one classical art form which was always highly valued, and a large but unknown number of ancient gems have never been buried and then excavated. Gems were used to decorate elaborate pieces of goldsmith work such as votive crowns, book-covers and crosses, sometimes very inappropriately given their subject matter. Matthew Paris illustrated a number of gems owned by St Albans Abbey, including one large Late Roman imperial cameo called Kaadmau which was used to induce overdue childbirths – it was slowly lowered, with a prayer to St Alban, on its chain down the woman's cleavage, as it was believed that the infant would flee downwards to escape it, a belief in accordance with the views of the "father of mineralogy", Georgius Agricola on jasper. Some gems were engraved, mostly with religious scenes in intaglio, during the period both in Byzantium and Europe.
In the West production revived from the Carolingian period, when rock crystal was the commonest material. The Lothair Crystal, clearly not designed for use as a seal, is the best known of 20 surviving Carolingian large intaglio gems with complex figural scenes, although most were used for seals. Several crystals were designed, like the Susanna Crystal, to be viewed through the gem from the unengraved side, so their inscriptions were reversed like the seals. In wills and inventories, engraved gems were often given pride of place at the head of a list of treasures.
Some gems in a remarkably effective evocation of classical style were made in Southern Italy for the court of Frederick II, Holy Roman Emperor in the first half of the 13th century, several in the Cabinet des Médailles in Paris. Meanwhile, the church led the development of large, often double-sided, metal seal matrices for wax seals that were left permanently attached to charters and similar legal documents, dangling by a cord, though smaller ring seals that were broken when a letter was opened remained in use. It is not clear to what extent this also continued practices in the ancient world.
Renaissance revival
The late medieval French and Burgundian courts collected and commissioned gems, and began to use them for portraits. The British Museum has what is probably a seated portrait of John, Duke of Berry in intaglio on a sapphire, and the Hermitage has a cameo head of Charles VII of France.Interest had also revived in Early Renaissance Italy, where Venice soon became a particular centre of production. Along with the Roman statues and sarcophagi being newly excavated, antique gems were prime sources for artists eager to regain a classical figurative vocabulary. Cast bronze copies of gems were made, which circulated around Italy, and later Europe. Among very many examples of borrowings that can be traced confidently, the Felix or Diomedes gem owned by Lorenzo de' Medici, with an unusual pose, was copied by Leonardo da Vinci and may well have provided the "starting point" for one of Michelangelo's ignudi on the Sistine Chapel ceiling. Another of Lorenzo's gems supplied, probably via a drawing by Perugino, a pose used by Raphael.
By the 16th century carved and engraved gems were keenly collected across Europe for dedicated sections of a cabinet of curiosities, and their production revived, in classical styles; 16th-century gem-cutters working with the same types of sardonyx and other hardstones and using virtually the same techniques, produced classicizing works of glyptic art, often intended as forgeries, in such quantity that they compromised the market for them, as Gisela Richter observed in 1922. Even today, Sir John Boardman admits that "We are sometimes at a loss to know whether what we are looking at belongs to the 1st or the 15th century AD, a sad confession for any art-historian." Other Renaissance gems reveal their date by showing mythological scenes derived from literature that were not part of the visual repertoire in classical times, or borrowing compositions from Renaissance paintings, and using "compositions with rather more figures than any ancient engraver would have tolerated or attempted". Among artists, the wealthy Rubens was a notable collector.