Unlike Roman micro mosaics, pietra dura—literally “hard stone,” it is also called “pietre dure” or Florentine intarsia—is not made of square or rectilinear tessarae but from thin bits of stone carved into specific shapes fitted together like a jigsaw puzzle. These pictures of flowers, birds, butterflies, or other insects were generally set into black marble and framed with metal. Artisans would use stone like malachite, carnelian, and quartz, which mimicked the natural webbing and color gradations of delicate wings and petals, to create stunning, realistic illusions.

Around 1860, the esteemed glass artisans of Murano developed their own style of micro mosaic jewelry, employing small bits of colored glass and multi-colored glass rods. These pieces have a distinct look that makes them easy to distinguish from the other two styles.

Architectural mosaics experienced their first revival in the 1500s, spurred by archaeological digs that revealed the breathtaking mosaics of ancient Rome. The Grand Duke of Tuscany, Ferdinando I de Medici, established the Grand Ducal workshop in Florence for the study of hardstone mosaic technique. Artisans who studied in Florence took their pietra dura skills all over Italy. Craftsmen in Prague and St. Petersburg attempted to re-create it.

The Florentine artisans used the natural color variations and inclusions in the minerals they worked with to turn their mosaics into stone paintings. Their techniques, along with related crafts such as marquetry, were adapted for aristocratic Baroque furniture and decor, from cabinets and commodes to screen panels and vases. Initially, Florentine mosaics were dominated by geometric patterns, but as techniques improved, allowing artisans to carve stone pieces into different shapes, the imagery became more figurative.

Micro mosaic jewelry has its roots at the Vatican, which had its own secret formula for making glass-like enamel tesserae for hundreds of years. Not long after St. Peter’s Basilica was erected in around 1600, damp clouds began to form inside the vast structure, ruining altar paintings made by some of the most famous artists of the day. Seeking a more durable material, Vatican artists noticed that architectural mosaics of ancient Rome had retained their color. They started look for ways to adapt mosaic techniques for copying paintings, which required developing thousands of hues of tesserae, also known as “smalti,” in a non-reflective material to give the appearance of a painted surface.

Eventually, they came up with 28,000 tesserae colors needed to accurately replicate most of the basilica paintings. By 1770, nearly all of them had been successfully copied in mosaic. Even now, tourists visiting St. Peter’s are often unaware the artworks they’re viewing are mosaic and not painted. In the mid-1770s, a few of these artists applied their skills to miniature mosaic art using teeny tiny tessarae, creating the first of what we know of as “micro mosaic.”

At first, the tessarae were rectilinear or square, but after a while, each piece could be individually shaped to resemble brush strokes. In the early 1800s, commercial mosaic studios opened in Rome, offering the rapidly growing tourist market micro-mosaic mementos of ancient Roman ruins. In Florence, artisans sold pietra dura jewelry, some of it reconstructed from antique fine furniture. In the early days, your average European traveler could only afford micro mosaics set into pill boxes and paperweights, whereas elaborate pictures, tabletops, and jewelry were made for aristocrats.

Perhaps the most important designer of micro mosiac jewelry was the Italian shop Castellani, founded in 1814 and run by artisan Fortunato Pio Castellani and craftsman and Dante scholar Michelangelo Caetani. Much of their work, including their cameo and micro mosaic pieces, was inspired by recent archaeological digs in ancient Roman and Egypt. Castellani’s unusually fine micro mosaic work was set in gold frames and adorned with Etruscan filigree and granulation. Often, the shop would incorporate Latin sayings in its mosaics, using Roman capitals surrounded by geometric designs.

English artisans also tried their hand at Florentine pietra dura, led by the sixth duke of Devonshire. Craftsmen based in Derbyshire cottages would set feldspar from recently discovered British mines within black Derbyshire marble to make cross- or oval-shaped brooches and pendants adorned with floral or insect motifs. These were popular with local tourists, including a young Princess Victoria, who bought such a piece when she traveled there in 1826.

The Victorian tourist trade, which brought great success to Italian micro mosaic jewelers, also brought about the downfall of the form. While micro mosaic jewelry clearly sold well, it was rarely mentioned in the jewelry design reports of the time. This indicates that tourists did not fully appreciate the level of workmanship that went into these pieces, and didn’t consider them art in the same way as, say, Egyptian revivalist or Japanese-style pieces. In the mid-1800s, artisans selling to tourists started to look for ways to save time and make their popular brooches more affordable, so the Roman tessarae got larger and larger, until they were visible to the naked eye and crudely set.

Around the same time, pietra dura craftsman cut corners by taking apart necklaces made earlier in the century and reconstructing them into brooches. Soon, Florentine artisans abandoned the more subtle stones of the past, and went for brightly colored and immediately striking materials like coral, turquoise, mother of pearl, and colored glass. These late-century brooches lacked the depth and realism of earlier jewelry. That’s why the delicacy and realism of a micro mosaic image can be used to date a piece and determine its value. Today, Roman micro mosaics are still made for tourists visiting Italy, but the tessarae are large and the workmanship is shoddy.

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