Shell, Sea Shells Value, Price, and Jewelry Information


Value

Shells are rarely of much value, unless carved as cameos. Values are based on eye appeal and carving quality when applicable.

The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

Information

DataValue
Crystallography Amorphous
Refractive Index 1.530 - 1.685
Colors All
Polish Luster Greasy to pearly
Fracture Luster Dull
Fracture Uneven to splintery
Hardness 3.5
Toughness Fair
Specific Gravity 2.70 - 2.89
Birefringence 0.155
Cleavage None
Stone SizesTo large
Heat SensitivityYes
Enhancements Dying to produce different colors, common. Detection, magnification. Stability varies from good to poor.
Transparency Translucent to Opaque
UV LongNot diagnostic
UV ShortNot diagnostic
Absorption Spectrum Not diagnostic
Phenomena Orient
FormulaMostly aragonite, CaCO3, plus some organic matter and water.
Pleochroism None

Ancient Shell Decoration

Sea shells are one of our most ancient decorations. Their earliest use was to string them into a necklace, or hang them from a cord as pendants. People still use them this way today.

Hishi Beads

We frequently find shells cut into hishi beads. This is a simple process that is preformed on beaches through out the world, but especially in the Philippines where most of our commercial hishi comes from. The shells are cut into squares and a hole drilled in the center. They are strung on a wire that is drawn tight. Then they are filed or ground into round shapes. A fine abrasive gives them their finish.

Hishi beads come in a wide variety of colors and sizes. They are very inexpensive and the gemologist is not likely to be asked to identify them.

Operculum

A number of shells are cut into cabochons or used for inlay. Of these, operculum is unique in that it produces an eye like cabochon.

Several types of shells have useful mother of pearl interiors. (Mother of Pearl is the iridescent layer found on the inside of several shells.) Mother of pearl is synonymous with nacre, being composed of alternate layers of aragonite and conchiolin.

Not surprising, our most common sources are the pearl producing oysters and mussels. In most cases, you will not be able to distinguish what kind of shell the mother of pearl came from.

Abalone is known for its exceptionally high orient. While found in many locations, the popular Paua varieties are found primarily in New Zealand. Three species are found in New Zealand, the Haliotis iris, H. australis and H.virginea.

Paua Shell

The Paua shell is the most colorful of all the abalone shells. Their colors include greens, pinks, purples and blues. Some even have gold or crimson toning.

Mother of pearl is used in its natural form, but it is frequently dyed as well. If it has a rich color, check with magnification for dye concentrations.

Shell Cameo

Cameos are primarily cut from helmet shells, conch shells, and the orange cassis rufa and cassis madagascariensis from Madagascar. However, any shell with a mother or pearl lining can be used. Cabochons are never of much value, but with the skill of the carving added in, cameo values can go over $100.

Assembled Cameo

Shell cameos are frequently imitated by plastic ones. The identification features of natural shells varies by variety, (see below.) Plastic imitations will feel warm to the touch and usually show mold marks. If there is some degree of transparency, you will see flow lines and gas bubbles, similar to glass. If all else fails, use a hot point test. Plastic emits an acrid odor, where shell will smell like burning hair.

A hot point test can damage the gem. If you are not familiar with the procedure, see “Destructive Tests” in our Reference Library.

Also, note that some cameos are natural, but assembled. They are easy to distinguish, because the carving doesn’t blend into the background as it does when they are carved from a single piece.

CAUTION! Shell dust is extremely toxic to breath. When working with shells, make sure you keep them wet and/or wear a dust mask.

Abalone Shell

 Identifying Characteristics

  • Abalone, exceptionally high iridescence, dark body colors.
  • Conch shell, pink to orange coloring, flame like structure.
  • Helmet shell, straight fibrous structure, concave back. When used for cameos, two color layers visible, white and orange or brown.
  • Mother of pearl, pearly luster and usually good to high iridescence.
  • Operculum, eye like markings on front, spiral growth on back.

Variety Names

  • Abalone
  • Conch
  • Operculum
  • Mother of pearl