Next to my own skin, her pearls. My mistress bids me wear them, warm them, until evening when I´ll brush her hair.

The opening lines of Poet Laureate, Carol Ann Duffy's poem called "Warming Her Pearls"

and one way to judge if pearls are natural, cultured or synthetic. (Read or listen to the full poem here)

JOHANNES VERMEER
MISTRESS AND MAID
(Dame en dienstbode)
c. 1666-1667
oil on canvas
The Frick Collection, New York

Pearls were an important status symbol of this age and they held for the educated Dutch art lover, a number of associations. In no other painting by Vermeer are there so many pearls. The mistress wears a pair of oversized drop earrings (artificial), a pearl necklace and strings of pearls in her hair.

When you first put them on natural and cultured pearls feel cold on the skin, they do warm up as you wear them. I can't find an explanation of why they are so cold but suspect it's to do with the poor conduction of heat. Synthetic pearls don't feel cold, unless they are made of glass. So another test is to rub the pearls on your teeth; natural and cultured pearls feel rough, synthetic ones feel smooth.
If the pearls are unstrung rub two gently together; if they offer resistance they are real or cultured pearls. If they feel smooth they are synthetic.

X-ray is the surest way to identify the type of pearl as it can differentiate between natural and cultured pearls - if you want to go to such lengths. Natural pearls are sold by weight (carat of pearls) while cultured pearls are sold by size (diameter of pearls).

Uniform natural pearls are extremely rare and very expensive.

The Baroda Pearls

In 1943, Maharaja Pratapsingh Gaekwar made headlines by marrying Sita Devi, his second wife. Referred to as “The Indian Wallis Simpson” by the Western media. Sita Devi received the jewels from the Baroda treasury including a seven strand natural pearl necklace.

The largest and most perfect pearls from the necklace were made into two large strands, consisting of sixty-eight graduated pearls, measuring approximately 9.47 to 16.04 mm, all matched in colour, lustre and shape and joined by a cushion-cut diamond Cartier clasp. In 2007 these were auctioned by Christies, along with matching brooch, earrings and ring, for the record sum of £4.5 million.

Read here in more detail.

Queen Elizabeth of Hollywood and Queen Mary1st of England
both wearing La Peregrina

La Peregrina is one of the most famous pearls in the world. Its history spans almost 500 years and it has passed from the African slave who found it at Pearl Islands in the Gulf of Panama to European Kings and Queens. Until recently, the pearl belonged to Elizabeth Taylor bought for her by Richard Burton as a Valentines gift - lucky girl!  She had it mounted on a diamond and ruby Cartier necklace. After her death it was auctioned at Christie's in New York, the bidding reached £7.1m. Watch the auction here.

Look after your pearls, they should be stored wrapped in soft cloth or in a soft-lined container to prevent them being damaged from harder items of jewellery.

Apply perfume, hair spray and other cosmetics before putting on your pearls to reduce the effects of these products on your pearls.
After wearing your pearls, wipe them with a soft damp cloth to remove any traces of cosmetic products or body oils.
The threads used to string the pearls are liable to stretch and break, be aware of this check the strands and get them restrung as necessary. 

Dear as the wet diver to the eyes Of his pale wife, who waits and weeps on shore, By sands of Bahrain in the Persian Gulf; Plunging all day in the blue waves; at night, Having made up his toll of precious pearls, Rejoins her in their hut upon the shore.

the words of Sir Edwin Arnold (journalist and poet 1832 -1904) using his poetic license to write a job description of a pearl diver.

I hardly know where to begin so much is written about pearls, from the wonderful imaginative myths of the ancients to the duller pragmatic accounts. I know I prefer to hear that the water that dropped from Venus’ body; as she emerged from the sea, was so affected by her beauty that it formed into Pearls. Slightly more romantic than: When a mollusc is invaded by a parasite or a foreign object that it can't eject, a process known as encystation covers the irritant in successive, concentric layers of nacre; a pearl is eventually formed.

The process of natural pearl formation is so rare that only 1 in 10,000 shells may produce a gem-quality pearl. As the layers of nacre tend to maintain the irregular shape of the original irritant, most natural pearls are irregularly shaped. Natural pearls which are round or spherical in shape are even more rare.

This baroque drop-shaped natural pearl weighing 239.7 grains (59.92 carats) 

 was sold for just under £160,000 at a Christie’s sale.

In the early 20th century demand for pearls led to Japanese scientists developing cultured pearls. By planting a polished bead made from special mussel shell along with a small graft of mantle tissue from a live oyster; the molluscs produce pearls. A typical fresh water mussel can produce up to 16-32 pearls at a time whereas the saltwater oyster can only produce 1 or 2 pearls at a time. Cultivation takes from two to four years depending on conditions, variety and whether it is a fresh or salt water mollusc.

My cultured pearls - I do  have matching earrings -
 I can't remember where I put them though....

Imitation or simulated pearls are entirely manmade. A bead is dipped into a mixture based on crushed fish scales known as "essence d’orient". This coats a bead and produces an imitation pearl. Other lower quality imitations may be made from plastic or ceramics. These are used for costume jewellery and provide an inexpensive way of imitating cultured pearls.

In my next blog, identifying "real" pearls, looking after pearls and more about mother of pearl.

If you really do want to read in detail about pearls take a look at this wonderful book written in 1908 The Book of the Pearl (available to read online).