8:41 AM

AVENTURINE



Aventurine is a form of quartz, characterised by its translucency and the presence of platy mineral inclusions that give a shimmering or glistening effect termed aventurescence.

The most common colour of aventurine is green, but it may also be orange, brown, yellow, blue, or gray. Chrome-bearing fuchsite (a variety of muscovite mica) is the classic inclusion, and gives a silvery green or blue sheen. Oranges and browns are attributed to hematite or goethite. Because aventurine is a rock, its physical properties vary: its specific gravity may lie between 2.64-2.69 and its hardness is somewhat lower than single-crystal quartz at around 6.5.


Aventurine feldspar or sunstone can be confused with orange and red aventurine quartzite, although the former is generally of a higher transparency. Aventurine is often banded and an overabundance of fuchsite may render it opaque, in which case it may be mistaken for malachite at first glance.

The name aventurine derives from the Italian "a ventura" meaning "by chance". This is an allusion to the lucky discovery of aventurine glass or goldstone at some point in the 18th century. Although it was known first, goldstone is now a common imitation of aventurine and sunstone. Goldstone is distinguished visually from the latter two minerals by its coarse flecks of copper, dispersed within the glass in an unnaturally uniform manner. It is usually a golden brown, but may also be found in blue or green.

The majority of green and blue-green aventurine originates in India (particularly in the vicinity of Mysore and Madras) where it is employed by prolific artisans. Creamy white, gray and orange material is found in Chile, Spain and Russia. Most material is carved into beads and figurines with only the finer examples fashioned into cabochons, later being set into jewellery.

Main markets for aventurine are landscape stone, building stone, aquaria, monuments, and jewellery.

9:29 AM

Star of India (gem)

The Star of India is a 563.35 carat (112.67 g) star sapphire, probably the largest such gem in the world. It is almost flawless and unusual in that it has stars on both sides of the stone. The greyish blue gem was mined in Sri Lanka and is now kept in the American Museum of Natural History in New York City.

The milky quality of the stone is caused by the traces of the mineral rutile, which is also responsible for the star effect, known as the effect of asterism. The tiny fibers of the mineral, aligned in a three-fold pattern within the gem, reflect incoming light into the star pattern.

History
In 1900, wealthy financier J.P. Morgan donated the Star of India to the American Museum of Natural History on Central Park West in Manhattan. On October 29, 1964, the famous golf-ball-sized stone was stolen, along with several other stones, including the Eagle Diamond and the de Long Ruby. The thieves unlocked a bathroom window during museum open hours, climbed in that night, and found that the sapphire was the only gem in the collection protected by an alarm — and the battery for that was dead. So they raked up the stones and fled the same way they came in. The stones were valued at more than $400,000. Within two days, the notorious cat burglar, smuggler, and one-time surfing champion, Jack Murphy (also known as Murph the Surf), was arrested along with two accomplices, later receiving a three-year sentence. Some months later, the uninsured Star of India was recovered in a locker in a Miami bus station. While most of the other gems were also found, the Eagle Diamond was never seen again.