April 24, 2019

If your birthday is in April, your birthstone—the gem associated with the month of your birth—is the diamond. The diamond is the hardest naturally occurring mineral, and also one of the most valuable natural substances. Because of its hardness, the diamond is the most lasting of all gemstones. In Europe, Japan, and North America, diamonds are widely used in engagement and wedding rings. Diamonds are also used in industry for cutting, grinding, and boring other hard materials. About half of the world’s natural diamonds are suitable only for industrial use. A small percentage are set in jewelry.

This photograph shows a naturally occurring diamond embedded in a sample of the rock kimberlite. Diamonds may be mined from pipe-shaped deposits of kimberlite, which fill the throats of extinct volcanoes. Natural diamonds are dull and must be cut by skilled jewelers to bring out the gem’s distinctive sparkle. Credit: © Matteo Chinellato, ChinellatoPhoto/Exactostock/SuperStock

Diamonds have been treasured at least since the days of the ancient Roman naturalist Pliny the Elder. He wrote: “Diamond is the most valuable, not only of precious stones, but of all things in the world.” Trade in diamonds was also prevalent in ancient India, and by the Middle Ages diamonds were fashionable accessories in several parts of the world. The diamond is a traditional birthstone for Aries (March 21-April 19), a sign of the zodiac. It is also a traditional gem gift for a 60th wedding anniversary—an event also called a diamond anniversary. In the past, some people believed diamonds possessed magical powers. According to legend, wearing a diamond could relieve fatigue or cure mental illness.

Diamonds are crystals that are made up almost entirely of carbon. Some diamond crystals have six faces, but most form octahedrons,which have eight faces. Natural diamonds probably form in Earth’s upper mantle—the zone beneath the crust—where high temperature and pressure cause carbon to crystallize. Diamonds are later brought to Earth’s surface by volcanic activity. The gems can be found in several places around the world, but the leading producers of natural diamonds include Australia, Botswana, Canada, the Democratic Republic of the Congo, and Russia.

Click to view larger image
Birthstones, according to tradition, bring good luck when worn by a person born in the associated month. Credit: WORLD BOOK illustrations by Paul D. Turnbaugh

According to tradition, a birthstone brings good luck to a person born in its month. Each birthstone also corresponds to a sign of the zodiac. The belief in birthstones may have come from a Bible story about Aaron, the first high priest of the Israelites. The story describes Aaron’s breastplate, which was decorated with 12 precious stones. Early writers linked these stones with the 12 months of the year and the 12 signs of the zodiac. The custom of wearing a stone that represented a person’s zodiac sign probably originated in Germany or Poland in the 1700′s.

May 17, 2018

On Tuesday, May 15, one of the world’s most beautiful and historic diamonds, the Farnese Blue, sold at auction in Switzerland for $6.7 million. The Farnese Blue is not the most expensive diamond on the planet—that honor currently goes to the $57.5-million Oppenheimer Blue, the world’s largest blue diamond. But $6.7 million is still a lot for a single gem, and the 6.16-carat pear-shaped Farnese Blue has had a fascinating journey that goes right along with the history books.

A silver marker is included in the box with the Farnese Blue diamond. In French, it reads: “Remarkable blue brilliant. This historical stone was offered by the Philippine Islands to Elisabeth Farnese, Queen of Spain, wife of Philippe V, great grandfather of the Comte de Villafranca, current owner of that stone.” Credit: © Sothebys

Tuesday’s auction at Sotheby’s in Geneva was the first public sale of the Farnese Blue, which had remained in the same family for centuries. Part of a bank-busting sale collection called “Magnificent Jewels and Noble Jewels,” the Farnese Blue was purchased by an unnamed private collector. Like many other famous diamonds, the Farnese Blue came from the historic Golconda mines of southern India.

Historically, the Farnese Blue can be traced back to Elisabeth Farnese, the queen of Spain from 1714 to 1746. At the time of her marriage to King Philip V in 1714, the Spanish monarchy was reeling from years of fighting in the War of the Spanish Succession. Badly in debt, the king appealed to Spain’s colonies around the world to provide wedding gifts for his new bride. Eventually, an enormous amount of gold and gems was loaded onto 12 ships, a so-called “Golden Fleet” that set sail from Cuba in August 1715, bound for Spain. Not long after leaving port, however, a hurricane destroyed all but one ship of the Golden Fleet—a ship carrying treasures, the Blue Farnese among them, collected by the governor of the Philippines, a Spanish colony at the time. Queen Elisabeth (and no doubt a frustrated King Philip) missed out on the bulk of the expensive gifts, but she had a shiny new blue diamond.

The Farnese Blue then passed down through Philippe, a younger son of Elisabeth and Philip who became the duke of Parma, Elisabeth’s hometown in Italy. The stone then went to Philippe’s son Ferdinand, the second duke of Parma. Ferdinand’s son Louis got the diamond before his brief reign as king of Etruria (present-day Tuscany, Umbria, and Latium) during the tumultuous years of the Napoleonic Wars (1796-1815). Louis’s son Charles, who after a roundabout path ended up as the Comte de Villafranca, left the Farnese Blue to his grandson, Robert, the last duke of Parma.

After the Risorgimento (the unification of Italy in the 1860′s), Robert lived with other deposed Italian dukes in neighboring Austria-Hungary, which was then ruled by Robert’s cousin, the Habsburg Emperor Franz Joseph. Robert’s son, Prince Elie, included the diamond in the wedding presents to his wife Maria Anna in 1903. The Austro-Hungarian Monarchy fell at the end of World War I (1914-1918), and with it went the royal status of the House of Habsburg. Maria Anna kept the Farnese Blue in the now private family, however, and the diamond passed down through successive generations until its eventual sale this week.

June 19, 2014

Evidence of a vast reservoir of water long thought to exist deep within Earth has been revealed in two recent studies. The reservoir, which may contain as much water as all of Earth’s oceans, is more than 300 miles (480 kilometers) below the surface in the mantle, the enormously thick layer of rock between Earth’s crust and inner core. One line of evidence for the reservoir was reported this month by scientists who analyzed seismic waves passing through the mantle beneath the United States. Another line of evidence, reported earlier this year, came from a battered diamond found in Brazil.

Scientists were quick to explain that the reservoir does not look like an underground sea. Instead, the water is locked within tiny grains of a kind of mineral called ringwoodite that forms in the searing temperatures and crushing pressures of the mantle. The water is not even a liquid or a vapor. It consists of hydroxide ions, negatively charged atoms of hydrogen and oxygen bound together. One scientists described the reservoir as a layer of “mushy rock.”

Beneath Earth's solid crust are the mantle, the outer core, and the inner core. Scientists can learn about the inside of Earth by studying how waves from earthquakes travel through the planet. (World Book illustration by Raymond Perlman and Steven Brayfield, Artisan-Chicago)

The seismic evidence was collected by scientists analyzing data collected by the Transportable Array (TA), an ambitious earth science observatory funded by the National Academy of Sciences. The TA consists of hundreds of portable seismic stations that measure waves of energy passing through Earth’s layers during earthquakes or other seismic events. Arranged in a grid pattern, the stations were rolled eastward across North America over a 10-year period. The scientists found that the speed of the waves changed as they passed through a part of the mantle called the transition zone. This suggested that the ringwoodite in this zone was melting. Finding evidence of melting at such an unusual depth, the scientists concluded, indicated that the ringwoodite was releasing water as it was carried deeper into the mantle.

The other study involved an analysis of a diamond shot from the transition zone to the surface through a volcanic eruption called a kimberlite. The diamond, which scientists said, looked like it had been “to hell and back,” contained a sample of water-bearing ringwoodite. It is the only known piece of ringwoodite ever found naturally on Earth’s surface. All other samples of the mineral, which lies too deep to be obtained by drilling, have come from meteorites or have been produced in scientific laboratories.

Scientists said that in addition for providing evidence of Earth’s hidden ocean, the research may shed new light on the movement of the tectonic plates that make up Earth’s outer surface. The findings also bolster the theory that the water in Earth’s oceans and lakes came from rocks that formed early in Earth’s history, not from icy comets that bombarded the surface.

Additional Woirld Book articles:

• Water cycle