The history of pearl hunting and pearl farming :

Pearl hunting :
For thousands of years, most seawater pearls were retrieved by divers working in the Indian Ocean, in areas like the Persian Gulf, the Red Sea, and in the Gulf of Mannar (by the ancient Tamils).
Starting in the Han Dynasty (206 BC - 220 AD), the Chinese hunted extensively for seawater pearls in the South China Sea.

Catching of pearls, Bern Physiologus (IX century)
When Spanish conquistadors arrived in the Western Hemisphere, they discovered that around the islands of Cubagua and Margarita, some 200 km north of the Venezuelan coast, was an extensive bed of pearls. One of them, the Peregrina, was offered to the Spanish queens. This pearl later became very famous when Richard Burton purchased it for his wife Elizabeth Taylor. Margarita pearls are extremely difficult to find today and are known for their unique yellowish color. The most famous Margarita necklace that any one can see today is the one that then Venezuelan President Romulo Betancourt gave to Jacqueline Kennedy when she and her husband, President John F. Kennedy paid an official visit to Venezuela.[citation needed]
Before the beginning of the 20th Century, pearl hunting was the most common way of harvesting pearls. Divers manually pulled oysters from ocean floors and river bottoms and checked them individually for pearls. Not all natural oysters produce pearls. In a haul of three tons, only three or four oysters will produce perfect pearls[citation needed].

The development of pearl farming :
However, almost all pearls used for jewelry are cultured by planting a core or nucleus into pearl oysters. The pearls are usually harvested after one year for Akoya, and 2-4 years for Tahitian and South Sea, and 2-7 years for freshwater. This mariculture process was first developed by Tatsuhei Mise and Tokichi Nishikawa in Japan.
The nucleus is generally a polished bead made from freshwater mussel shell. Along with a small piece of mantle tissue from another mollusk to serve as a catalyst for the pearl sac, it is surgically implanted into the gonad (reproductive organ) of a saltwater mollusk. In freshwater perliculture, only the piece of tissue is used in most cases, and is inserted into the fleshy mantle of the host mussel. South Sea and Tahitian pearl oysters, also known as Pinctada maxima and Pinctada margaritifera, which survive the subsequent surgery to remove the finished pearl are often implanted with a new, larger nucleus as part of the same procedure and then returned to the water for another 2-3 years of growth.
Despite the common misperception, Mikimoto did not patent the process of pearl culture. The accepted process of pearl culture was developed by a team of scientists at Tokyo University between 1907 and 1916. The team was headed by Tokichi Nishikawa and Tatsuhei Mise. Nishikawa was granted the patent in 1916, and married the daughter of Mikimoto. Mikimoto was able to use Nishikawa's technology. After the patent was granted in 1916, the technology was immediately commercially applied to akoya pearl oysters in Japan in 1916. Mise's brother was the first to produce a commercial crop of pearls in the akoya oyster. Mitsubishi's Baron Iwasaki immediately applied the technology to the south sea pearl oyster in 1917 in the Philippines, and later in Buton, and Palau. Mitsubishi was the first to produce a cultured south sea pearl - although it was not until 1928 that the first small commercial crop of pearls was successfully produced.
The original Japanese cultured pearls, known as akoya pearls, are produced by a species of small pearl oyster, Pinctada fucata martensii, which is no bigger than 6 to 7 mm in size, hence akoya pearls larger than 10 mm in diameter are extremely rare and highly prized. Today a hybrid mollusk is used in both Japan and China in the production of akoya pearls. It is a cross between the original Japanese species, and the Chinese species Pinctada chemnitzii.[7]