Rock Lab

APPENDIX 5

Rock Lab

Rock Lab Equipment

Rock Saw

Draw Saw/Slab Saw

Drill Press

Roto Tap

Sieves

Trim Saw

Grinding Tables

Polishing Tables

Standard Thin Section Preparation and Cleanup Procedures

Cutting and Preparing Billets

Fill the basin beneath the rock saw with water to the level of the first step using the hose near the sinks. Do not fill to the brim

Cut a billet out of your handle sample. The billet should be no larger than the size of a microscope slide and approximately 0.5 inches thick

Grind the side of the billet that is going to be glued to the slide on the grinding wheels. The purpose of this step is to insure the billet is very flat before gluing it to the slide. Start with 400 grit. Wet the wheel with water. Fill the spout attached to the wheel with water, stir, and adjust the facet so that one drop is released every 1-2 seconds. Stir often to keep grit from settling out of solution. Move the billet back and forth across the radius of the wheel while grinding. Use a straight edge (razor blade) and hold up to the light to check for flatness

Repeat step 3 using the 600 grit wheel

Turn on heat pad before mixing epoxy as some heat pads take time to warm up.

Mix epoxy (5 parts resin and 1 part hardener). Resin and Hardener are both found in the yellow flammable materials cabinet. Place an empty foil mixing cup on the scale and zero the scale. Add resin and note the weight. Add 1 part hardener and mix

Set mixture on heat pad and remove in 30-60 seconds

Apply a thin line of epoxy along the center of the billet (it does not take very much epoxy). Gently, place the frosted side of the slide on the billet. As the cement spreads outward, it should expel bubbles. If bubbles persist, gently press a pencil eraser to the surface and work out the bubbles

Let the epoxy cure (rock side up), about 12 hours

Cleanup

Drain the rock saw into the metal bucket. Dump the water onto the lawn outside or slowly into the floor drain by the sinks (keep rock chips out of drain). Using the hose, thoroughly clean and remove all rock chips, dust, and mud from the basin and the sliding platform. Wipe the blade clean and then dry with a paper towel

With water and a paper towel, clean the grinding wheels until completely clean. Make sure they are completely clean and dry to prevent rust

With a mop or broom, clean up any water and rock debris on the floor

Discard unwanted rock chips into the bucket labeled for rocks. Do not discard rocks or rock chips outside

Be sure all cabinets are closed to keep the supplies clean

Trimming Billets and Thin Section Completion

Make sure the tub beneath the trim saw (in the cabinet) is filled with water, but not overflowing. Turn both the pump and the power switches on. Turn the two black knobs on the back of the tub until water is released onto the saws

Wet the top white area of the saw arm and place the slide against the wetted area. Cut the bulk of your mounted billet off

Use the right saw to grind the slide down to a final thickness of approximately 1 mm. By turning the knob on the left side of the trim saw tub, you can continually grind down your slide thinner and thinner. Be very careful not to over grind and be sure to make complete passes across the wheel to insure uniform grinding. Don't take large jumps in thickness, just a tiny turn of the adjustment knob at a time until you stop hearing grinding. Ever so often rotate the slide and continue grinding. Periodically hold the section up to the light to check thickness or use a petrographic microscope to see if grains are exposed

Play it safe and stop using the trim saw if you are unsure of the stability of the rock on your slide. Using a glass plate, water, and 600 grit silicon carbide powder, polish your slide to 0.03 mm using a figure eight motion. Again, be careful not to over polish. Continually check your slide under the microscope for the correct thickness based on the known birefringence of quartz, feldspars, or other minerals

Once you have the desired thickness, clean the remaining epoxy and grit from the slide with rubbing alcohol

Use the metal pen to inscribe a sample number on the slide. Fill this grooved writing with ink if you desire. You can also write the sample number on the slide with pencil and the Canada Balsam will protect the writing

Using a small drop of Canada Balsam on the center of the slide, gently place a cover slip on top of the slide. Smooth with the eraser end of a pencil and cure on heat pad for about 10 minutes. See Canada Balsam bottle for more specific instructions

Final Cleanup

Wash glass grinding plate with water and dry with paper towel

Prop the trim saw up with a wood block, allow to drain. If excessive silt persists, clean with hose or cups of water. If necessary, drain water out of the catch basin below the saw with a plastic cup

Dry any wet saw blades

Be sure all cabinets are closed to keep the supplies clean

Turn off all lights, saws, and make sure all the doors are locked

Polished Thin Section Preparation Procedures

For consolidated material

Cut standard billets (see above)

Affix to standard glass slide with epoxy. Tip: Frosted slides always work better; they can be easily frosted using 200 grit powder on the slow wheel

For unconsolidated material

Glass slide must be frosted, preferably coarser than the manufactured frosted slides. This can be done using 200 grit powder on the slow wheel

Affix loose grains to frosted side of slide with epoxy. Tip: UV epoxy (Norland optical adhesive, no. 61) is preferred as you can move the grains around before setting it almost instantly under UV light. Also make sure grains are close together, not spread out over the section

Polishing Routine

1. Cut your billet down to a few mm using the left blade on the trim saw

2. Move your slide over to right side blade on 600 grit wheel (vertical grinder)

3. Begin thinning your sample by slowly passing the slide back and forth across the grinder. Make complete passes across the wheel to insure uniform grinding. Don't take large jumps in thickness, just a tiny turn of the adjustment knob at a time until you stop hearing grinding. Ever so often rotate the slide and continue grinding. Periodically hold the section up to the light to check thickness or use a petrographic microscope to see if grains are exposed. Microprobe sections don't have to be the perfect thickness (30 µm) but they should not be much thicker than a standard thin section. If you need a perfect 30 µm thick thin section, you may want to finish grinding your sample by hand using a piece of 600 grit paper (gray 8" carbimet paper disc) on a piece of plate glass with petrographic microscope nearby. Note: Some people affix a few grains of quartz to the edge of their slides to use as indicators of the correct thickness under the microscope

4. Clean samples with soap and water and move to the horizontal wheels at the far end of the rock lab (next to the flammable materials cabinet)

5. On Wheel One (wheel farthest from flammable materials cabinet)

a. Affix a 1000 Textmet polishing cloth to wheel

b. Spray well-shaken 3 µm Metadi Supreme Polycrystalline diamond suspension onto polishing cloth (green oil-based solution) and spread around with thin section. You don’t need very much of this, just a few sprays. You can use the Metadi extender to spread the diamond grit rather than using more solution.

c. Place thin section in plastic holder and turn on wheel. This wheel turns very fast so get a good grip. Periodically remove sample and check that scratches are being removed

d. When all scratches from the 600 grit wheel have been removed (sample will still look dull), you are done

e. Clean sample with soap and water (or general purpose cleaner like 409) and sonicate for about 15 seconds before moving to the next wheel. This is extremely important!

f. Clean sample holder the same way

6. On Wheel Two (wheel closest to flammable materials cabinet)

a. Affix a Mastertex polishing cloth to wheel (very fine cloth)

b. Apply well-shaken 0.05 mm Alumina suspension (white, water-based solution) to cloth. This can be re-suspended on cloth or diluted with deionized water (don’t use tap water)

c. Polish sample using the same technique as above. The sample will become shinny. A perfect polish is best assessed under reflected light where all exposed grains are flat and white. This step takes about one minute

d. Clean sample with soap and water (or general purpose cleaner like 409) and sonicate

e. Clean sample holder the same way

Note: If either wheel is too fast or it becomes too warm (usually after polishing 6+ sections, the wheel starts to smoke) you can always polish by hand using consistent figure eight motions. This will obviously take longer, perhaps 5 minutes per polishing solution.

Supplies for making polished microprobe mounts

Buehler Catalog #	Description	Price
40-7618	Texmet 1000 polishing cloth (8” diameter), 10 pk	$43.00
30-5108-600-100	Carbimet 600 grit paper discs (8” diameter), 100 pieces	$81.00
40-7738	Master Tex polishing cloth (8” diameter), 10 pk	$37.00
40-6377-032	Masterprep alumina 0.05 mm suspension	$48.00
40-6631	Metadi Supreme polycrystalline diamond suspension, 3 mm, 8 oz	$61.00
406016	Metadi extender solution	$19.00

All supplies are from Buelher Scientific; 1 800 283 4537; prices quoted on 7/30/2001

Norland Optical Adhesive (UV epoxy), no. 61, 1 oz: www.norlandprod.com; $25.00/bottle (~50 thin sections)

Northern Arizona University

College of Engineering, Forestry and Natural Sciences