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- With an agate mortar and pestle
- With a Spex shatterbox
- With a Spex mixer mill 8000M (tungsten carbide, hardened steel, agate, or alumina ceramic)
- With Retsch MM400 mill (agate)
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There are two mixer mills located in X-Ray Prep. Both mills operate very similarly but do have slight differences The older 8000M and the newer Retsch400, (Figure 9; Figure 1016) . The 8000 is featured on the top and the 8000M on the bottom. are discussed below.
Figure 9: 8000M mixer mill. (A) Safety latch (B) Minute timer (C) Seconds timer (D) Start button (E) Pause/Stop button (F) Timer countdown LCD display.
Figure 10: 8000 mixer mill. An older simplified version of the 8000M. Featured are the safety latch, timer dial, and start/stop button in the middle of the dial.
The main difference between the two mixer mills is the timer. The 8000M timer uses 2 buttons to adjust the minutes (Figure 9B) and seconds (Figure 9C), 2 separate buttons to start (Figure 9D) and manually stop (Figure 9E), and counts down time on the LCD display (Figure 9F). To operate the 8000 mixer mill, turn the knob to the desired time and press the "Start" button in the middle. That button will also stop the mixer mill. The dial does not move automatically, so if it is turned to 5 minutes it will stay there. The dial does not need be set back to 0 to work.
Grinding Vessels
There are three types of grinding vessels available for the 8000M mixer mill: alumina ceramic, tungsten carbide, and hardened steel (Figure 11). Tungsten carbide and steel vessels are better for more robust grinding, and alumina ceramic is better for minimizing contamination. Check with the Science Party to see which vessel type is preferred.
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Cleaning the Vessels
Clean the grinding vessels with a toothbrush and DI water. In some cases the vials are still dirty or have sample stains on them. If so, take a small amount, approximately 5 mL, of silica sand and grind it in the mixer mill for ~3 minutes. Then pour out the sand and clean the vessel with DI water and a toothbrush or Greenie Meanie. Lay out cleaned vessel parts on a Kim Towel and dry with a Kim Wipe. The cork rings take a longer to dry, so collect fresh, dry rings before grinding the next sample.
Then can now pack the samples.
Retsch MM400 mill
Figure 16: Retsch MM400
Grinding Jar
Figure 17. Agate grinding jars and ball.
Each grinding jar has the main jar, the lid and ball, and the white teflon spacer. Use the spacer to avoid damaging the agate. The inside of the jar and lid are lined with agate and the ball of made of agate. Poor freeze dried soft sediment (not hard rock) sediment grains into the jar. Fill the jar half way to three-fourths of the way up with sample. Place one ( can do two) grinding balls in the jar. Clean off any of the sediment sample with a kimwipe that has gotten onto the jars threads and screw the lid on. Be mindful not to cross thread the lid to the jar.
Figure ##. Agate grinding jars with teflon spacer and the bent metal spatula for removing
Loading the Jar into the Grinding Mill
Place closed grinding jar horizontally in the clamps. Verify the pin is in closed position and tighten the clamps by turning the handle until the jar is securely tighten (hand tight is good). Close lid and select desired program to run.
Figure 18 MM400 Grinding jar clamp
Starting the Mill
After grinding jars are secured in clamps, the pin is in the closed position and the clear cover is closed it is time to select grinding settings. Program 1 (A) is currently set for 12 min at 25 1/s. This setting is good for clay rich material. Softer sediments such as CaCO3 typically need less time. It is important to only grind soft sediments in the agate jars and hard material should be ground in the shatter box. After Grinding cycle has completed twist knob counter clockwise and pill pin up and into its open position( Figure 18a). Unscrew clamp and open jar to verify grind size. If sediment is still too coarse regrind.
Figure 19 A) Preset programs. B) The shaker frequency C) The time grinder is set for D) The start and stop
Transferring Powder
After grinding is complete remove grinding jar from clamps. rotate black screw counter clockwise a quarter turn and pull the pin up into the open position (Figure 18a). open pin is in the open position unscrew black knob until grinding gar is loose enough to remove. Unscrew grinding jar, poor powder onto weigh paper or directly into clean and labeled sample bag.
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