Gem Profile- Mother of Pearl

by Judy Ellis

So, I have been sitting her singing "Molly Malone" to myself as I've been writing this week's Gem Profile. Why, you ask? Because this week we're learning about Mother of Pearl. Okay, so maybe "Molly Malone" doesn't really relate to Mother of Pearl, or MOP as we sometimes abbreviate it, but just wait and you may be humming along with me soon.

Pearls and Mother of Pearl

Most of us are familiar with the beauty and luster of pearls, and even Mother of Pearl (MOP). But what is MOP, how does it differ from pearls, and how did it get the name "Mother of Pearl"?

Pearls and MOP differ in only one aspect: shape.

MOP is the inner lining of a mollusk's shell. It protects the creature from bacteria and disease and helps reinforce the shell against damage.

To understand how Mother of Pearl is formed, it helps to look at the development of the mollusk and the shell in which this soft-bodied invertebrate lives.

Pictured: Mother of Pearl pendant wire-wrapped by Joan Madouse in silver-filled wire.

Linda Pope wrapped this abalone shell, carved in the shape of a fish tail, in gold-plated wire and embellished it with Swarovski crystals. She calls it "Whale of a Tail"!

How Mother of Pearl Forms

The mollusk starts life in a soft shell called an umbo, a small rounded oval. As the animal grows, it quickly outgrows the umbo and secretes nacre to expand its home.

The nacre forms in concentric rings, like tree rings, and thickens outward as the animal grows. I wish I could do this with my home; five teenagers definitely need more space!

The outer layer of the shell, called the peristacum, is the first layer to form around the animal. This organic layer of conchiolin is made of keratin proteins, similar to our skin, but it is dark brown, black, or blue and very hard.

Barbara Rymarquis wire-wrapped this abalone shell in sterling silver. This pendant is reversible!

The next layer to form is the ostracum, made of tiny hexagonal crystals of calcium carbonate in the form of aragonite. These crystals align parallel to each other and are held together by conchiolin.

The aragonite layer provides stability to the flexible protein layer, while the conchiolin helps prevent fractures, making the shell very strong. Even though these layers are chemically the same as nacre, they are formed differently and make up the outside of the shell.

The final layer is the hypostracum, or Mother of Pearl. It is formed similarly to the outer shell, but the aragonite layers are thinner and not parallel. This layer resembles a brick wall, with thin conchiolin acting as mortar to hold the aragonite "bricks" together.

Because the aragonite in this layer is made of platelets rather than crystals, it is transparent and interacts with visible light. Some light is reflected while other light is absorbed, giving MOP its iridescence. The word "iridescence" comes from the Greek word for rainbow, iris.

Teresa McMahon wrapped this Mother of Pearl shell in gold-filled wire.

What Mother of Pearl Comes from

Some of the mollusks that provide Mother of Pearl are gastropoda, bivalvia, and cephalopoda. These include mussels, conch, paua, abalone, and shells like the nautilus.

Some shells, like paua and abalone, have beautiful banded nacre, while others, like the nautilus, have a smooth MOP layer with little or no banding.

Mother of Pearl makes stunning jewelry and can be dyed in many fun colors, which we'll explore in the next week or so.

Irisha Patterson created this sterling silver and gold-filled wire frame for a Mother of Pearl cameo, inspired by Dale Armstrong's book, Wirework.

How to Care for Mother of Pearl

Care for your MOP the same way you would pearls: no acid, no steam or ultrasonic baths, and be careful around objects that could scratch the surface.

MOP is about a 3.5 hardness and can scratch fairly easily.

Irisha Patterson also wrapped this mother-of-pearl cameo in sterling silver and gold-filled wire, with a different effect.

Now you probably know why I've been humming "Molly Malone" all day: well it's because of the cockles and mussels creating Mother of Pearl of course!

Resources & Recommended Reading

Mother of Pearl on Pearl Guide www.pearl-guide.com

Gem Profile- Mother of Pearl

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