Published: July 2012
An assembled stone is one that is constructed out of two or more materials. The components may be natural or man-made materials, but most commonly are a combination of both. This category includes creations such as doublets and triplets, inlays, mabe pearls and reconstructed gem materials. There are three common reasons why such pieces are made: 1) to protect or make wearable small or delicate gem materials; 2) to provide an inexpensive simulant for a solid natural gem; 3) to create an entirely new category of gem product.
Most gem lovers are familiar with doublets and triplets, especially the opal variety. The color band of opal frequently occurs as thin layers. Although beautifully colored, some stones are too thin and fragile, making them unsuitable for jewelry. By cementing one of these thin layers to a strong backing (black onyx, opal matrix, or other dark material), two goals can be achieved. The strong backing provides the thickness and strength needed for setting in jewelry, and the dark color makes the translucent opal layer look like black opal. The color play in the gem material is enhanced against this dark background.
An opal doublet must still be set and worn with care, as the exposed surface is still opal. Further, solvents can attack the bonding layer over time. Well-done pieces look wonderful, and make affordable, reasonably durable opal jewelry.
An opal triplet is merely a doublet that has an additional clear layer (usually quartz or glass) on top for added protection. Ammolites are often assembled in this way to protect their fragile nature. In effect, it forms a sort of “sandwich.” Triplets may contain opal mosaic, synthetic opal, organic material such as leaves and feathers – or most any natural or artificial material.
Doublets and triplets are also created to combine the best of two natural gem materials. Rutilated quartz top over a lapis base takes advantage of the beautiful blue of lapis and the shimmering golden threads of the rutilated quartz. Faceted clear quartz over a turquoise base is also stunning. The possible combinations are infinite.
It is not uncommon to see natural materials combined with synthetic materials. A faceted stone with the top half composed of natural sapphire and the lower half made of synthetic sapphire will appear the color of the finer synthetic, while exhibiting natural inclusions near the surface. These types of doublets have been presented as very convincing imitations to unaware buyers for years. Glass was commonly fused to a thin garnet slice on top, in order to benefit from the greater hardness of garnet, but this was done before the ability to produce much better imitation gems and is rarely seen today. These types of doublets may be glued or fused together. In some cases they are obvious, others are difficult to detect without experience and magnification.
Soudé stones are a type of assembled gem that can imitate most any transparent, faceted gem material. They are a type of triplet with a top and bottom layer bonded together with a transparent, colored, bonding layer. The colored bonding agent is considered the third component. They are most commonly green to imitate emerald, and may contain a light to colorless beryl (the mineral group for emerald) layer on top to fool some tests. Today’s Soudé stones are most commonly two layers of colorless synthetic spinel with a green bonding layer, but they can be any color.
Newer quartz triplets are composed of natural quartz (for hardness) top and bottom layers, and contain a decorative layer of various designs that create an entirely new look in gemstones. While some may resemble natural materials, most are created for fun, fashionable and affordable looks, while incorporating natural gem materials.
Mabe pearls are a type of assembled cultured pearl. Rather than forming as a loose pearl, they form as a blister on the inside of a pearl mollusk shell. The blister is cut away from the shell, the hollow area is filled and then a plain mother-of- pearl backing is applied to the bottom. In some cases, two mabe pearls may be attached back to back, giving the appearance of a single pearl. There is always a visible seam with mabe pearls, and care must be taken when cleaning to not weaken the bond.
When small, thin pieces of gem materials such as opal or shell are set into recesses within metal, the term inlay is used. Inlay opal generally uses smaller pieces of opal that are set with a black bonding agent to appear like black opal. They are, in effect, much like a doublet, with the jewelry itself becoming the dark backing. Inlay illustrates all reasons for making assembled stones, in that they allow use of small or thin pieces, which might otherwise be unsuitable for jewelry, lighter colored opals are made to imitate the rarer black opal, and they also provide a unique and lovely gem product.
Reconstructed materials are those that are composed of smaller pieces of natural gem materials that are bonded together. The best-known reconstructed material is turquoise, but many opaque materials can be similarly treated, including coral. Small pieces of natural material are packed together and bonded with a strong polymer. In some cases, dye may be added to the pieces themselves or to the bonding agent. Another method of producing reconstructed gem materials involves heat. A good example is pressed amber. Numerous smaller pieces are heated close to the melting point and pressed together forming a single, larger piece. Reconstructed materials offer an affordable alternative to natural, single-piece gems. Other gems may fall under the category of assembled, such as hybrid and composite materials, but will be handled under different topics. These materials may seem similar, but they are actually a newer generation of treatment in which the join between the various components is not visible. All of these assembled gem materials described here, the join or seam of the materials is visible with the naked eye or with some magnification.
The care and wearing recommendations for assembled stones vary with the materials involved and method of assembly, but certainly ultrasonic and steam cleaning should be avoided. Current bonding agents are extremely durable, but older ones are known to degrade with time. Anything that might attack or weaken the bonding or otherwise compromise the integrity of the piece is to be avoided, including high temperatures. It would also be prudent to have such stones removed when jewelry containing them is repaired or sized. In general, erring on the side of caution is wise.