Whistling Stones

If a volcano erupts explosively and casts fluid lava high into the air, the lava is dispersed by the wind, giving rise to particles of various sizes from ash to molten blobs of lava up to 15 feet wide called volcanic bombs.
Often volcanic bombs are still soft enough to change shape during their flight through the air. Their motion in flight tends to give those elongated shapes and smooth surfaces. Rounded masses are common, and sometimes the ends are twisted into a spiral. Volcanic bombs frequently flatten or splatter when they land. If the bombs are the size of a nut, they are called lapilli, Latin for “little stones,” and form strange gravel like deposits that litter the countryside. If volcanic bombs cool in flight, they form a variety of shapes. The various types of volcanic bombs are described as cannonball, spindle, bread-crust, cow dung, ribbon, or fusiform, depending on their shape or surface appearance.
Bread-crust bombs, which often reach several feet across, are named for their crusty appearance, which is caused by gases escaping from the bomb while the outer surface is hardening. The bombs might also be hollow or have numerous cavities formed by bursting gas bubbles on the surface. Sometimes volcanic bombs actually explode when they hit the ground as a result of the rapid expansion of gas in the molten interior when the solid crust cracks open on impact. Often, volcanic bombs spin wildly through the air, causing them to whistle like incoming cannon fire.
Beneath the Pacific Ocean near French Polynesia, strange single frequency notes were found emanating from clouds of bubbles billowing out of undersea volcanoes. The notes were among the purest in the world, far better than those played by any musical instrument. The sounds were at first thought to have come from secret military testing or perhaps some strange marine creature. Even whales are known to emit loud calls to one another. However, no explosion or animal was capable of sounds of such singular notes.
The low frequency of the sound also meant the source had to be quite large. Further search of the ocean depths uncovered a huge swarm of bubbles. When undersea volcanoes gush out magma and scalding water, the surrounding water boils away into bubbles of steam. As the closely packed bubbles rise toward the surface, they rapidly change shape, producing extraordinary single frequency sound waves.
In the desert, a curious feature of sand dunes is an unexplained phenomenon known as booming sands. The sound occurs almost exclusively in large, isolated dunes deep in the desert or well inland from the coast. The noises can be triggered by simply walking along the dune ridges. When sand slides down the lee side of a dune, it sometimes emits a loud rumble. The sounds emitting from the dunes have been likened to bells, trumpets, pipe organs, foghorns, cannon fire, thunder, buzzing telephone wires, and low-flying aircraft.
The grains found in sound-producing sand are usually spherical, well rounded, and well sorted, or of equal size. The sound appears to originate from some sort of harmonic event occurring at the same frequency. However, normal land sliding involves a mass of randomly moving sand grains that collide with a frequency much too high to produce such a peculiar noise.

Joseph Kieffer
http://jewelryuk.org
from: http://hand-crafted-jewelry.com