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- Place a small amount of sample powder in the center of a quartz or single crystal quartz disk.
- Add 2–3 drops of 70% 70 % isopropyl alcohol or distilled water to the sample. Note: Isopropyl dries faster than water.
- Spread the sample to a thin layer using a glass rod. The slurry should be spread evenly across the disk. If there is not enough material to cover the entire disk, concentrate the sample in the middle of the disk where the X-rays will contact the sample.
- Place the sample in the dessicator desiccator to dry before running in the XRD.
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Clay Separations focus on separating the clay size fraction, <2um<2 µm, from the rest of the material. In order to get only that size fraction we prepare the sample in a different way. Do not freeze dry samples waiting for clay separations. If the samples have already been dried the treatments will still work but using fresh, wet samples is easier. Below are outlined various treatments and methods we do on board.
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This is the recommended treatment for carbonate removal. The process is slightly more involved than the HCl procedure, but far less damage is done to the mineral structure. The following steps are from Kitty Milliken (UT-Austin).
- Place sample in in centrifuge tube with 25 ml of 10% 10 % Acetic Acid for at least 1 hour to decarbonate (it helps to place the centrifuge tubes on the agitator in the cold room)
- Centrifuged Centrifuge for 15 mins at 1500 rpm, decant and wash with 25 ml of nanno pure water (3X to remove all Acetic Acid)
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The probe power source is shown on the left in Figure 20. Flip the "ON" Switch (Figure 20A). The settings are already set to our needs. To run as is, press the "Start" button (Figure 20B). If you need to change a setting, see the "Set" button (Figure 20D) and the "Mode" button (Figure 20C). From these two panels, you have access to the power, time, and displayed units. For more information, reference the Manufacturer Manual located in the side pocket of the dismembrator case.
- Add ~25 mL of a 1% 1 % borax solution into the centrifuge tube. Borax prevents the sample from flocculating. Too much Borax however will increase flocculation.
- Put the tube into the bottom clamp inside the dismembrator case. When satisfied with the positioning, press the "Start" button on the probe power supply (Figure 17B). If the material does not appear to be circulating throughout the whole tube or the tube is heating up, adjust the probe position and start the dismembration over.
- Let samples settle overnight (~12 hours). The next morning, the material should be separated out with the clear liquid filling most of the tube and sediment filling the bottom cone.
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- Add 25 ml of 1% Borax solution to the clay plug
- Dismembrated sample (machine is auto set on time), to remove the >2 um µm clay fraction
- Centrifuge for 4 mins at 750 rpm, decant the suspended liquid into a separate centrifuge tube (you should end up with a ~full centrifuge tube of suspended clay)
- Repeat steps 1-3 on the remaining >2 um µm fraction
- Centrifuge the <2 um µm fraction for 15 mins at 1500 rpm to remove the Borax solution
- Decanted and add 25 ml of nanno pure water
- Centrifuged for 60 mins at 3000 rpm, the liquid decanted before loading onto a zero background silica disk.
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For the double peaks of Kaolinite and Chlorite, heating the sample only suggest that one of the minerals is present, it will not give final and complete results for a sample that contains both Kaolinite and Chlorite. In order to determine which mineral is present, an additional treatment is necessary.
- Take the <2um <2 µm clay fraction, this should be rinsed and free of any treatments, in centrifuge tube add ~20ml ~20 ml of 1N HCl
- Vortex the sample to completely dislodge all material before pouring sample into a 100ml 100 ml beaker, add stir bar once sample is in place
- Set hotplate to 300C 300 °C (boiling point of HCl is ~101, but in order to maintain a continuous boil the hotplate needs to be much hotter)
- Set the stir RPM below 100, this is only to keep the material suspended within the HCl
- Start time once the samples have come to a complete boil, leave for 2 hours - add more HCl as necessary (DO NOT, let the sample go dry and burn)
- Once the sample has boiled for 2 hours, turn off hot plate and allow sample to return to room temperature before pouring beaker contents back into a clean centrifuge tube, rinse beaker with DI water to collect all material
- Centrifuge down for 15 mins at 1500 rpm, decant acid and rinse with 25 ml nannopure (3X)
- After samples has been washed 3X and is free of HCl, centrifuge for 60 mins at 30 rpm
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