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c. If a rock stratum is not of even incremental thickness <br />e.g., 8 feet of sandstone, the stratum should be sampled <br />from 0-4' and 4-8'. <br />d. Y7hen an obvious change in properties, such as penetra- <br />tion of the weathered zone below the land surface, oc- <br />curs at a point within a rock type, the two zones are <br />recorded and sampled as different rock members. <br />3. After proper subdivision, each entire sample unit is pul- <br />verized to pass a 10 mesh (2.Omm) sieve. <br />4. The sample is then riffled to obtain a representative <br />sample of approximately 500 gms. and then dried at 50- <br />60°C. overnight. <br />5. The sample is then pulverized to pass a GO mesh (0.25mm) <br />sieve and riffled to approximately 100 gms. and retained <br />in 4 oz. sample bottles. <br />6. The remaining sample is retained in metal containers and <br />stored in a dry and convenient area for future referral. <br /> <br /> <br />6-2-3 <br />