Unit Four - Drilling Methods
2. Ore Deposits
Lab Activity

-  Plastic terrarium

-  Mortar sand (2.5 gallons) and colored terrarium sand (1/2 gallon)

-  7/16 “ or ½ “ Thin wall, rigid, clear plastic tubing, cut to a length of 15”

-  Plastic beaker.

-  Water

-  Graph paper

-  Black fine Sharpie

-  C-thru plastic ruler w/1/10 “ scale

-  Answer Sheet AS16

-  Answer Sheet AS17

-  Answer Sheet AS18

1. Fill the terrarium approximately 3 “ deep with mortar sand.  Add enough water to just saturate the sand.  Shape the top surface of the mortar sand so it slopes about 30 – 40 ^o.
2. In a plastic beaker measure 4 cups of colored sand.  Note the exact volume, and convert this to cubic inches.  Saturate the colored sand with water.
3. Make a layer of wet colored sand, approximately 0.5 to 1.5 inches thick, and approximately 6  inches wide x 9 inches long.  Form the colored sand layer on top of the mortar sand, making the layer slanted and somewhat irregular in shape, but generally tabular.   Make one edge visible on one of the long sides of the terrarium. 
4. Cover the colored sand with mortar sand 2 to 4 inches thick, so the top surface is flat and  approximately 8 inches above the floor of the terrarium.
5. Carefully add more water in the corner area to completely saturate the sand at the top surface.

1. Make a slight groove in the sand for each of the drill lines.  Make the two dill lines parallel to each other and to the sides of the terrarium, and spaced approximately 3 inches apart.  Make each line 12 inches long, and label the drill lines A – A’ and B – B’. 
2. Starting at the bottom end of the tube, make black marks every inch, for seven inches.  Label the first mark, near the center of the tube,  “0”.  The next mark below this will be labeled 100 ft. Continue labeling the rest of the marks to the “700 ft” at the bottom of the tube.  The scale will represent depth (in feet) below the surface.
3. Drill holes will be drilled at the 3”,  the 6”  and the 9” positions on each drill line.  Drill the first drill hole at the 3” mark on Line A – A’.  Drill a vertical hole by carefully pushing the tube down, until  the “0” mark on the tube matches the upper level of the sand. 
4. Place your thumb over the end of the tube to seal it from leaking air.  Pull the tube up and completely remove it from the sand.  Continue to hold your thumb on the end of the tube to keep the sand from falling out of the tube.
5. Note the intercepts (in feet) for the upper and lower contacts of the “ore zone”, and write them on Answer Sheet AS18..  Draw the drill hole on the drill section for Line A – A’ (Answer AS16),  by drawing a vertical line 7” long, starting at the drill collar location shown for DH1.  Show the intercepts for the ore horizon on the drill hole using a heavy black line.
6. Drill another drill hole at the 6 inch mark on Line A – A’ using the same technique.  Note the intercepts.  Draw the vertical drill hole at the location for DH2, and highlight the intercept.
7. Follow the same procedure for DH3, which will be at the 9 inch mark on Line A – A’.
8. Sketch lines between the drill holes to connect the intercepts across the space between the drillholes.  Draw a vertical line halfway between DH1 and DH2 to indicate the boundary between  Block 1 and Block 2.  Draw another vertical line halfway between DH2 and DH3 to indicate the  boundary between Block 2 and Block 3.
9. Drill holes along Line B – B’ at the 3”, 6” and 9” marks, and note the intercepts on the drill  section for  Line B – B’ (Answer Sheet AS17).
10. Connect the intercepts between the drill holes on Line B – B’, and draw vertical lines to show the boundaries between the blocks.

1. Block 1 is centered by DH1.  The thickness of the block can be measured on the drill section.The area of influence of the drill hole is 1.5 inches.  This means that Block 1 has a width of 3” and a length of 3”, and is centered on DH1 (at the 3” mark).
2. The scale of the model is 1 “ = 100 ft.  The area of the block is 3 “ x 3 “, or 9 square inches, or 900 square feet.  Multiply the thickness of Block 1 times 900 to determine the volume of Block 1 (in cubic feet).  Write the answer in the space on Answer Sheet AS18.
3. Follow the same procedure to determine the volumes of the rest of the blocks, and write the  volumes in the spaces on Answer Sheet AS18. 
4. Determine the total volume by adding the volumes for the individual blocks. Compare this volume with the volume of the sand which was measured by your teacher.

1. The tonnage factor is 12 cubic feet per ton.  Divide the volume by 12 to determine the total tonnage for Block 1, and write the answer in the space on Answer Sheet AS18.
2. Follow the same procedure to calculate the tonnages for the rest of the blocks.
3. Add up the tonnages for the six ore blocks, and write it in the space on Answer Sheet AS18.

1. Multiply the grade x tonnage for each block.  Write the results on Answer Sheet AS18.
2. Sum the results you obtain in the space indicated on Answer Sheet AS18.
3. Divide the sum by the total tonnage.  The result is the weighted average grade.

1. The “resource” is the total amount of a commodity in an ore deposit.  For a gold deposit, the  “resource” is a statement of the total amount of ounces contained within the deposit.  Multiply the weighted average grade times the total tonnage.  The result is an estimate of the total amount of contained ounces of gold in the deposit.

Field Methods | Geochemical Methods | Geophyscial Methods | Drilling Methods | Petroleum Exploration

DMTC Home | ISM Home