Cutting & Crushing Sample Preparation Techniques

10” rock cutting saw

Utilizing one of the plastic beakers the thin section lab (K-11) make a solution (400 to 500 ml) using 1 part cutting fluid (in 5 gal. drum) to 5 to 10 parts water. Make sure the drain hose is crimped and now pour the solution onto the top of the saw and let it drain down into the compartment below. Turn on saw and make sure blade is making contact with cooling solution. NOTE: if you trim more than four or five rocks during one session, you will have to add more solution as you proceed. Also as you cut the rock sample, do not push or force the sample unduly; proceed at a smooth, relatively slow, orderly pace. If the blade and the rock sample bind (blade stops turning) turn motor off immediately and free sample.

Object 1: to cut a thin section blank of this dimension ~1/8 to 1/4 inch thick, free of all alteration.

Object 2: to cut one or more rock slabs, free of all alteration, which add up to 200 to 400 grams. Aphanitic rocks should be at the lower end of the spectrum while porphyritic or phaneritic rocks should be at the upper limit. These slabs should be less than 1.5 to 2 inches thick so that they will fit into the jaw crusher.

When finished, drain the saw; clean up the saw completely, using sponge and paper towels. Dry off cutting surface with paper towel before leaving room. Clean table top on both sides of trim saw.

Bico “chipmunk” rock crusher, or "the jaw crusher"

1. Jaw crusher (Make sure hood is on during crushing and cleaning procedures to keep the dust level down to a bare minimum.) Thoroughly clean between samples using acetone, kim-wipes, and the air-hose.

Bico rock pulverizer/grinder

2. Mullite grinder (Alumina ceramic plates; not iron or steel or WC) (Make sure hood is on during crushing and cleaning procedures to keep the dust level down to a bare minimum.) Thoroughly clean between samples using acetone, kim-wipes, and the air-hose.

Sample splitter

3. Split sample at this stage into two halves, using the geochemical sample splitter. You may need to split twice or even three times to end up with 50 to 100 grams of whole rock powder. Now, onto Step 4 with one portion that will be crushed into a fine powder; saving the other portion as a coarse fraction in a labeled plastic container (tub) of appropriate size. Label both the lid and the container. Please note: hood should be on during the splitting procedure)

 

Shatter box

4. Spex Shatter Box ceramic sample grinding container. This apparatus is quite brittle; do not drop. Thoroughly clean between samples using acetone, kim-wipes, and the air-hose. Clean the rubber gasket using just the kim-wipe, no acetone on the rubber gasket please.

 

Shatter box shaker

The picture to the left documents the placement of the sample-grinding container within the shatter box itself. Be sure the raised circular area on the top of the sample container mates perfectly with the cup-part of the hold-down lever arm. This device is to prevent the sample container from coming loose during the violent shaking that is about to commence when the shatter box starts its gyrations.

Laboratory sieve

*Note: When All the powder passes the 80-mesh sieve screen, you're done. Transfer the powder to a labeled container of appropriate size.

Reminders:

1. Thoroughly clean each of the grinding machines with acetone and kim-wipes. Do not use acetone on large rubber O-ring in the shatter box ceramic grinding vessel.

2. A dust mask is available for use. Please use them at all times.

3. Label both container lids and bottoms (outside) with sample number.

4. If you are uncertain about a particular step, STOP. Ask before you proceed any further.

Safety Warning: Acetone poses health and fire hazards. Get more information.

Don’t forget to wear your PPE (personal protective equipment)!