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O Seismograph records. Colorado Quarries has only monitored one shot <br /> which indicated both PPV and PSPL were well within allowable range. <br /> As mentioned above, the minimal amount of explosives needed to <br /> achieve fragmentation of the obsidian maintains both a low vibration and <br /> air blast. <br /> GEOLOGY <br /> Included is a geologic report of the Silvercliffe area. Volcanic activity <br /> occurred in this area approximately 40 million years ago. Vertical and <br /> horizontal movement has shifted the obsidian flow. At the mine site the <br /> obsidian is cropped out at the surface yet less than 3/8 mile the bed is <br /> 150' below the surface. <br />