Reference

The majority of cameos, both those carved in natural materials and those molded in a man made substance, are set so that the back of the cameo is visible, except when set in an item where covering over the back is necessary or desirable: box lids; lockets and fob seals; many rings.  When the back of a cameo set as a brooch or pendant is covered, the question arises of whether something on the back--flatness or a depression; bubbles or the pock marks left by bubbles--is being hidden.  These are telltale signs that might give away the true nature of a piece that is quite convincing as shell, lava or hardstone when seen from the front.  Backs may be covered completely or with more decorative filigree.

This shell cameo of The Three Graces would appear to be the exception that proves the rule.  However, Howard had the ornamental back added so that he could have the cameo engraved when he gave it to Kay as a memento of their visit (perhaps honeymoon?) to Italy in 1947.

If the indistinct lines of the "carving" did not already give it away as a molded piece, one might think the cameo to the right was hardstone with a carnelian base layer.  The covered back and the attachment of the cameo to its setting by means of a small rivet are sufficient to identify this as an artificial piece.

It is not always the case that a cameo gets a setting worthy of it.

The shell cameo of Aurora on the left, a lovely example of the carver's art, is set in a simple brass setting.  The ornate 18k yellow gold setting shown on the right houses a molded glass cameo.

 This lava cameo is competent, no better, and of Ceres, a common subject, but has certainly been given the royal treatment: 14k gold set with diamonds and sapphires, embellished with enamel.

Cameo Times is deeply grateful to Julie at the Fontaines Pétrifiantes of Saint-Nectaire, France, for the following detailed information on the technique employed for creating cameos and other items using the calcium carbonate rich water of the local hot springs:

When it's raining the water is going deep down into the ground (in Saint-Nectaire, the water goes approximately 3,000 meters deep). But because of the heat and the carbon dioxide, the water is expelled to the surface as a spring.  Our water is hot naturally (35°C) and very rich in calcium carbonate (we have 2g/liter of limestone). The limestone is perfectly dissolved in the water.  But scientists know how to extract the limestone from the water: by creating a water ventilation [system].

After years of research, in 1821 Jean Serre (Eric Papon’s ancestor) created the first fontaine pétrifiante at Saint-Nectaire: a ladder where the spring [water] rich in limestone could go through and run such as a waterfall!  His research helped him to understand that more the ladder is high, more the piece of limestone left by the water is small at the bottom of the ladder! And the deposit is rare. The more you are at the top of the ladder, the more the pieces of limestone are bigger and numerous!

Nowadays, Eric Papon, (maître artisan en pétrification and owner of the factory) still uses his ancestor’s technique to create two types of objects:

The first one is crystallization: he puts a pottery at the top of the ladder, he turns it every morning so that the limestone layer is the same all around the object during 3 months. When the thickness is enough, he puts the petrified object out of the water, and when it's dry, it is sold in our shop.

The second one is encrusted mould or also called limestone cast: He uses a matrix in copper which was created by an artist, thanks to the gutta-percha he creates a mould.  Making the mould is complicated and needs time and experience.  We have 3 ladders with different heights (14 meters - 25 meters - 28 meters) The more the ladder is high, the more the limestone carbonate [particles] will be small.  Our craftsmen know exactly where to put the mould to get the greatest piece of limestone.  First he puts the moulds at the bottom of the ladder to get the little pieces of limestone which will create all the details such as the face of your cameo.  But if he leaves the moulds always at the bottom, he would need years to get enough thickness.  So after 1mm of limestone is inside the mould (which needs 3 months) he ascend the mould step by step to get bigger piece of limestone and a stronger limestone cast!  That is why the back of your cameo has a depression and is rough!

As with the pottery, he needs to turn the moulds to be sure that air bubbles or gas bubbles won't be stuck inside the limestone which would create a hole inside the limestone cast. 

For the color, our springs are very rich of iron.  To get a white limestone, before the ladder, the spring [water] goes inside a wood shaving gallery to filter naturally the iron!

To get a cameo, we need 12 months of work! And your cameo comes from our place as we recognized the frame.

To know if cameos are in limestone, just look at the back! If it looks like yours [the first cameo shown in the main article], it's limestone!

The eBay seller of this cameo ring also acted as his own GIA (Gemological Institute of America) certified appraiser and assessed the cameo as being shell.  This is an example of damage being informative: one never sees the nose knocked off of a shell figure without there also being damage to the background; such traumatic rhinoplasties are more the rule than the exception for hardstone cameos set in rings.  The other features that distinguish this hardstone piece from shell will be covered in those sections.

In general, artificial materials tend to be denser, more opaque and less translucent than natural materials.  However, there is so much variability, this factor may only be a minor one when assessing a cameo's material.

 The great majority of cameos we see are carved in some variety of helmet shell.  The assortment shown to the left includes, starting top left: a piece of the sort often identified as oyster shell because of the greyish background, which is really the white layer ground down very thin; one with a background so thin it almost looks like shellac; one very average in color and thickness; bottom left, a piece with a very dark background of average thickness; and a piece of greater than average thickness.  Dark or light, thick or thin, all are moderately to highly translucent.

Thetis dipping the infant Achilles into the River Styx to make him invulnerable to wounds is carved in as large and thick a slab of conch shell as they come.  Still, a fair amount of light can come through.

Although quite large and substantial, this piece in angel skin coral, which does not seem as though it would allow any light to pass through, does indeed exhibit some translucence when held against a moderately bright sunlit window.

Held against the same window, this coral-look resin piece is opaque.  But it is also thicker than the angel skin cameo.

Bacchus here is at least a half inch (1 cm or more) at his thinnest points.  Like his resin imitator, his thickness makes him opaque too.

Lava and its imitators are all opaque.  The brown lava plaque of Night has quite a thin background layer, the lava glass dancer is a bit thicker, but neither allows light to pass through.