#junebirthstone

Sumptuous gold surrounding cultured pearls and purple sapphires. Earrings by Paula Crevoshay.

Non nacreous pearl from the “spiny oyster”:
6.97 ct bicolored white and pink Spondylus pearl with a beautiful reflective blue coloration a flame structure when viewed in certain directions under a single white light source. Photo by Robert Weldon/GIA.
The spiny oyster shells occur in reds, oranges and purples depending on their diet. Because of their vibrant colors spiny oyster shells are often used in jewelry; especially Native American jewelry.

Shelled mollusks produce a “pearl” when a microscopic irritant is trapped within its mantle folds. The mollusk creates a pearl sac to seal off the irritation. This is a part of the mollusk’s defense mechanism against a potentially threatening irritant such as a parasite inside the shell, or an attack from outside that injures the mantle tissue.
The mollusk’s mantle deposits layers of calcium carbonate in the form of the mineral aragonite or a mixture of aragonite and calcite that are held together by an organic horn-like compound called conchiolin. This combination is called nacre. Natural pearls are nearly 100% nacre (calcium carbonate and conchiolin). This secretion process is repeated many times, eventually producing a pearl.
Natural pearls are quite rare. This means that hundreds of pearl oysters or mussels must be gathered and opened just to find even one wild pearl. For this reason pearls were able to fetch extraordinary prices in the past. With the advent of cultured pearls there was a dip in the value of pearls as a reaction to the fact that they were now available to more than just the elite classes. In recent years there has been a steady increase in the value of natural pearls as buyers are drawn to the rarity of natural pearls once again.
“Gem” quality natural pearls are still very rare. Values are determined by size, shape, color, quality of surface, orient and luster.

*A pair of belle époque natural pearl and diamond pendent earrings, circa 1910
Sold by Bonhams in 2006.*

•Feldspars are the most diverse and widespread minerals in the earth’s crust.
•Moonstone is the most familiar gem-quality member of the feldspar group.
•Moonstone is a part of the feldspar group, and is a variety of the species orthoclase within that group.
•Moonstone is a composite of two feldspar minerals, orthoclase and albite. After the orthoclase and albite have come together they cool and separate into alternating layers that are stacked on each other.
•Moonstone is known for having an ethereal misty glowing look. This phenomenon is called adularescence.

•Adurlarescence is occurs when light falls between the stacked layers of orthoclase and albite and scatters it.

•Rainbow moonstone has a multicolored adularescence over a light bodycolor. However it is not actually moonstone. It is a variety of labradorite (often from Madagascar) and rainbow moonstone is a trade misnomer.

*The necklace features moonstones and labradorite set in silver. It was made by Danish Designer Georg Jensen between 1915-1927 and currently resides at the Victoria & Albert Museum.*