MOONSTONES
The finest moonstones are feldspar gemstones occurring in Burma and Ceylon. Both countries provide rough remarkable for its high degree of translucency, almost water-clear in some specimens, and the presence of minute inclusions which give rise to a beautiful silvery or blue sheen. Any rough requires careful inspection before purchase because of the tendency of native dealers to attempt to dispose of unsuitable material.

Much of the rough is partly split along two prominent cleavage planes or sometimes into plate-like fragments which, at first glance, seem satis¬factory for cabochons. Unfortunately, such thin pieces often display the moonstone sheen only on the thin edges. This means that any gem cut from them would have to be so small that it would scarcely pay for the cost of cutting. If these fragments are cut in any other way, with the idea of obtaining larger gems, the sheen will be badly off center.

Much less troublesome is the feldspar moonstone which has recently appeared from India in the form of large blocky fragments. While good-sized gems may be cut from them, they seldom compare in translucency or strength of sheen to the fine moonstones of Burma and Ceylon.

SUPERIORITY OF WATERWORN OR WEATHERED ROUGH
Much high-quality material occurs in the form of pebbles and boulders which have eroded from the rocks originally enclosing them. Sometimes they are found near the place of origin, but at other times they are washed into streams and rivers and subjected to severe pounding before coming to rest in a gravel deposit. Only the soundest crystals and masses can survive this combined attack of weathering and stream wear, and it is for this reason that gravel beds rich in gems are the particular target of knowledgeable gem miners. It can be truly said that nature has tested each piece and destroyed those found wanting.

Stream-worn material is therefore likely to be of very high quality and includes the gem pebbles from Ceylon and Burma mentioned earlier, various durable gem species such as topaz, tourmaline, beryl, and chryso-beryl from alluvial deposits in Brazil and elsewhere, and waterworn agates such as those from the Montana river deposits. Nephrite jade and jadeite are famous for providing very fine material from pebbles and boulders. In fact, the older Chinese jade carvers vastly preferred alluvial material, either nephrite from the stream gravel deposits of Turkestan, or the jadeite boulders from Burma. These were viewed as having proved them¬selves tough enough to produce the most delicate carvings.

Weathering need not be connected with stream wear as is shown by the loose nodules of chalcedony found lying on the ground in many places in the world. The agate nodules and geodes of southern Brazil and northern Uruguay, vein sections of chrysoprase in Australia, petri¬fied wood in Arizona, and peridots and garnets in New Mexico and Arizona are some examples of gemstones weathered from their original deposits. Nature has destroyed the enclosing rocks in a gentle yet irre¬sistible fashion, leaving behind the more durable gem material. As far as freedom from defects is concerned rough of this kind can be of top grade because it has been treated gently during the long cycle of erosion. However, if cracks existed in the material from the time of its formation, they may still be present after it has lost its enclosing rock and, as a general rule, the quality of the material is not as high as that found in stream gravel deposits where a more severe elimination process has taken place.