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Table of Contents
Before being crushed in the X-Press, hard rock samples for ICP analysis are polished (Figure 1.1 and 1.2) and cleaned in a sonic bath at least three times (for 10-15 minutes each): the first round of cleaning is with isopropyl alcohol and the following rounds are with DI water (Figure 1.3, see ICP Sample Preparation for further details). Hard rock samples for XRD analysis do not usually need to be polished before being crushed.
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Figure 1. Polishing and cleaning hard rock samples
Crushing Samples in the X-Press
The X-Press is a motorized hydraulic press that crushes hard rock and highly compacted sediment samples into smaller pieces.
Preparing the X-Press area
- First, clean the X-Press and counter with simple green and isopropyl alcohol. Lay down a Kimwipe or sheet of paper on the counter.
- Next collect the following supplies that make up the 'crushing unit' of the X-press (Figure 2). Materials are located in the drawer labeled 'X-PRESS SUPPLIES' in the X-Ray Prep Area in the Thin Section Lab.
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The crushing unit is now assembled and we can start crushing samples with the X-Press (Figure 4A).
Crushing Samples
Place the crushing unit inside the X-Press (Figure 4B) in the middle Safety Note: Always wear safety glasses and hearing protection. Do not stand directly in front of the X-Press while it is operating. Never leave the X-Press unattended while using. Do NOT take the instrument above 10 tons of pressure.
Place the crushing unit inside the X-Press (Figure 4B) in the middle of the metal platform (Figure 4A, arrow A). Slide the polycarbonate door down in the vertical indents (Figure 4C). Note: The polycarbonate door sits on two interlock switches that enable operation. If the door is not fully closed or pressing down on these switches the machine will not work. Tighten the jackscrew (Figure 4A, arrow B) until it rests firmly against the aluminum die. Tighten the pressure relief handle until just tight with a clockwise turn (Figure 4A, arrow C).
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Crush the sample by holding down the toggle switch (Figure 4A, arrow D). The motor and pump can be heard and the pressure will rise (Figure 4A, arrow E). When the toggle is released, the sample will sit under that pressure. Do NOT leave a sample under pressure for any reason. For most samples ~5 tons of pressure is enough force to crack it. If you find the need to go near 10 tons, try rotating the sample onto another side and repeat the process again. Taking the pressure up greater than 10 tons can cause the discs and the core liner to shatter, as well as contaminating the samples and creating a safety hazard.Safety Note: Always wear safety glasses. Do not stand directly in front of the X-Press while it is operating. Never leave the X-Press unattended while using. Do NOT take the instrument above 10 tons of pressureTaking the pressure up greater than 10 tons can cause the discs and the core liner to shatter, as well as contaminating the samples and creating a safety hazard.
After the sample has cracked, release the toggle switch. To remove the unit, loosen the pressure relief handle (Figure 4A, arrow C) by rotating it counter clock wise and hold down the toggle switch. The pressure gauge should read zero and the metal platform will lower down. Do not leave the platform up, always make sure to lower it back down after crushing a sample. When the platform is level with the surface let go of the toggle switch and unscrew the jackscrew. Then slide the polycarbonate door up and remove the unit. The pieces can be poured into a labeled bottle that will eventually hold the finely ground powder. From here the pieces will then be put into the Shatterbox vessels.
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When the shatterbox cycle is done, open the lid and remove the vessels, placing them on the counter. Open the grinding vessel and with clean tweezers take a bit of the powder and feel it against the inside of your wrist. The sample should feel like talc powder. If it does not, repeat the shatterbox cycle. A 1-3 minute cycle is enough for most of rocks.
Transfer powder into Vial
Disassemble the vessel carefully wearing Nitrile gloves. Clean off any powder on the lid or puck with a Kimwipe or Teflon spatula. Carefully remove the puck from the vessel. Pour the sample onto a clean piece of weigh paper. If any powder remains, use a cleaned Teflon spatula to dislodge it.
Never use metal to dislodge or scrap out sample material, as any grooves or scratches in the vessels will increase the risk of contamination.
Cleaning the Grinding Vessels
Vessels must be cleaned in between samples and after all samples have been run for the day. Vessels should never be put away wet. This alters and tarnishes the grinding vessel.
In Between Sample Runs
- Wearing nitrile gloves, wash the individual pieces of the grinding vessels with tap water and a small piece of a scouring pad (no soap). Rinse with DI water.
- After each piece is washed, dry it with a Kimwipe, immediately spray it with isopropyl alcohol, and wipe it down with a Kim Wipe. Do not use the ship's compressed air line to dry pieces as the air is too dirty.
- Lay the pieces on, and cover vessels with Kimwipes.
After the last run for the day 1.
Take a scoop of quartz sand and put it in your vessel(s) and run it as you would a sample for several minutes (~3 min should be adequate).
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Remove the vessel and empty out the sand. Scrub the pieces with tap water and a scouring pad and rinse with DI water. Dry with a Kimwipe, and then spray with isopropyl alcohol and wipe down with Kimwipes. If your vessel is particularly dirty run a combination of quartz sand, a little hot water and detergent (Borax). This can be run for several minutes. A thick paste will form and then you clean it as normal.
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XRD Sample Preparation Hard Rock - September 27, 2022