Major Element Technique
A. Lithium tetraborate - whole rock powder preparation
1. Thoroughly clean and dry several glass sample bottles (24 ml glass bottles from Thomas Scientific) and lids if clean bottles are not already available. The final cleaning step is always to rinse in acetone and lay bottle on its side and turn the plastic caps up on a paper towel for the purposes of drying.
2. Weigh out 3.6000 grams +/- 0.0002 of Li2B4O7 onto a piece of weighing paper (previously weighed and tared) and transfer to a clean glass bottle. Label glass bottle with magic marker (not lid) with sample number followed by WR (whole rock).
3. Weigh out 0.4000 grams +/- 0.0001 of whole rock powder onto a piece of weighing paper (previously weighed and tared) and transfer to the same bottle as in 2.
4. Carefully rotate sample bottle in your hands so as to mix the powders without letting them touch the lid.
5. Make sure you have labelled the bottle!
6. Mix sample for 10 minutes in the mixer-mill.
7. If you stop at this step without going onto Part B, store bottle in a dessicator.
B. Fuse sample to make glass disc per demonstration given by your instructor. Key factor to always remember-- mix your liquid sample three times in the Pt crucible; once at the 3 minute mark, again at 5 to 6, and the 3rd time just before pouring into the Pt lid. Also, be sure to incline the Pt crucible in the flame before pouring to break the surface tension between liquid and metal so that most or all the sample will be used in casting the glass disk. You must mix three times to insure sample homogeneity.
Do not forget the following items:
1. When fusing sample always wear safety glasses.
2. Add two or three drops of LiI solution to powder after it has been transferred to Pt crucible, from small labelled plastic squeeze bottle .
3. Be extremely careful in cleaning Pt lid! DO NOT SCRATCH!!!
4. With a magic marker, label sample number on concave slide of glass disc - side which cools in contact with air.
5. Place 1/2 of a small kimwipe in the bottom of a pillbox and put glass disc, label side up, into the container and cover with lid. Do not label the pillbox itself.
6. Store pillbox in a dessicator.
7. Clean the glass bottles and caps you used in distilled water, using scrub brush. Rinse in distilled water and then rinse in acetone and let dry in air on a paper towel for an hour or so. Lay the bottles on their sides to dry. Recap and put back into the storage trays.
