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Gold/Mining/Energy : BANDORE
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To: rdww who wrote (1676)3/24/2001 12:59:24 PM
From: E. Charters  Read Replies (2) of 1692
 
If hit with a sledge, a boulder no matter how large (even 15 feet in diameter) will give a characteristic drummy dull sound. An outcrop will ring soundly. The key is in the ring and how it resonates. With large bodies the sound travels quite a ways in the rock and rings because the vibration is not attentuated. In small bodies the sound quickly dampens with reflections and has a lower characteristic, so they give a duller sound. Underground you quickly learn that even huge pieces of loose give that characteristic hollow dull thump when tapped with a scaling bar. Send your boys back out and tell them to listen to the rock. (Another key is that a vertical or nearly vertical erosion surface in several or even two sides means the chances are the rock is either a hillock or a boulder. Other keys are presence and oreintation of striae and fissility or shear orientations. )

An ear on a steel or glass on a nearby rock outcrop (50 to 100 feet) will pick up the ring of the hammer if it is not a boulder.

EC<:-}
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