University of Vermont

From whole rock to <1 mm particles:

Materials:

paper grocery bag or loose paper

rock hammer or sledge hammer

plastic sample bags (ziploc)

type LA8 jaw crusher

type UA Bico pulverizer (plate grinder)

hardened steel plates

Safety:

eye protection at all times

ear protection for jaw crusher and pulverizer

respirator with HEPA filter for jaw crusher and pulverizer

Procedure:

WORK WITH ONE SAMPLE AT A TIME TO PREVENT CONFUSION OR MIS LABELING!!!!

1) Wire brush sample to remove lichen and adhered material. Place rock samples into a paper bag or wrap with paper. Using a rock hammer or sledge hammer, break sample into approximately 1 x 3 inch fragments. To avoid contaminating samples with foreign rocks or pieces of rock from other samples, make sure to clean the bag or paper before crushing next sample; if any particles are left on the bag or paper, replace the paper with new. Work in an area free of other rock material. Sweep between samples. Place rock fragments into a plastic sample bag and label it.

2) Using the jaw crusher, grind the rock fragments into 0.5-1 cm particles; collect ground material in metal tray from plate grinder and transfer to plastic oil pan.

3) !!!NOTE!!! BIN BELOW PLATE GRINDER WILL FILL QUICKLY.

EMPTY IT OFTEN OR YOU WILL LOOSE SAMPLE FROM OVERFLOW

Next, grind each sample separately in the plate grinder. Pre grind about 50 g of material and discard. (This should remove any carry over from the previous sample). The goal in this step is to obtain monomineralic grains without ending up with a large amount of powder, though some powder will inevitably be produced. Set the plates 0.5 mm apart to obtain 0.5 mm size, monomineralic grains. Slowly pour some of the sample into the mouth of the grinder and wait for the sample to be fully ground; grinding is complete when no sound of grinding rock can be heard (5-10 seconds for 100 ml of rock). Pour in another aliquot. Use sieves to check your grain size distribution if in doubt. Bag samples in clean sample bag and label. NOTE

4) Clean the jaw crusher and the area around it with a small broom between each sample, vacuum to remove remaining dust. Blow out with compressed air. Vacuum. The plate grinder must also be thoroughly cleaned between each sample. Use a shop-vac to clean every part of the plate grinder exposed to the rock or powder. Then blow out with compressed air. The plates need to be scrubbed with a dry, stiff brush. GOOD CLEANING IS ESSENTIAL. REMOVE ALL TRACES OF THE LAST SAMPLE FORM THE ENTIRE GRINDING CABINET.