Searles Lake Gem and Mineral Society
See  Flyer  for dates and times
Blow Hole Field Trip CANCELLED
The Blast               The Blow Hole Minerals

The crystals found during this field trip, especially the rare hanksite which is found at only one other place in the world, occur within the Upper Salt at a depth of 30 to 50 feet beneath the salt surface.  This depth, plus the fact that the lake brine level is almost at the surface, means that without help from Searles Valley Minerals it would be impossible for our Gem-O-Rama visitors to find anything.
The preparations for this field trip begin about one week before the show.  Searles Valley Minerals technicians begin by choosing a site where good crystals are thought to be available and where there is a large enough flat area to allow field trip parking.  Then a line of six to eight hole locations are marked, each about 60 feet from it's neighbors. A rotary drill bores 12 inch diameter holes into the salt body at each location.  These holes, which are typically 50 feet deep,  provides the access needed to recover the hanksite and other crystals.
The second step occurs three days before the field trip when Explosives Ordinance Technicians from the U. S. Navy at China Lake arrive on site to blast the holes. The blast objective is to loosen crystals within the target depth so they can then later be "blown" onto the surface.  After examining the site and talking with the IMCC geologists and technicians, the crew prepares a detailed blasting plan.

The Navy crew measures and marks the primer cord so that the high explosives can be accurately set at the depths where the crystals are to be loosened. 

Blocks of exposive are taped together at several points along the primer cord to provide explosive force at several depths.This allows the required number of blocks of explosives to be used while still minimizing damage to the crystals.  The explosions along the primer cord are timed with a slight delay between clusters with the top cluster going off first and the bottom cluster last.  This expands the salt body near the top of the salt bed, giving room for the lower salt to expand into.

Weights are hung on the bottom end of the primer cord to make sure the explosive assembly goes all the way to the bottom of the hole. A weight and primer cord/explosive assembly is then carefully lowered into each hole.  Sandbags are also placed on the primer cord at the top of the hole to keep it in place.

Go to The Blast.
Go to The Blow Hole Minerals
Go to  Gem-O-Rama Site Map

Searles Lake Gem and Mineral Society
P. O. Box 966
Trona, CA 93592-0966
Phone (760) 372-5356
FAX (760) 372-4799

Home  |  Site Map  | Revised 05/15/2021

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