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lapping lepidolite slabs

I recently purchased a 12 inch Covington lap and made an attempt at finishing several smaller slabs of lepidolite (actually the slabs are a mixture of quartz and fine grained lepidolite). I have had many cabochons of this material done overseas so know it can be brought to a fairly nice polish. However, it did not take me very long to figure out that I need some tutoring!!!!! I started out by using 200 and 600 grit silicon carbide (it is gray-blackish material) and quickly found that the apparent contaminating iron oxides are an issue .....It took oxalic acid in a warm sonic bath to get the staining out! Rather than wander around reinventing the wheel ....here are some questions I could use some help with before I continue:

1) Given my experience thus far with silicon carbide ....should I switch to aluminum oxide? Perhaps the silicon carbide would do jasper slabs ok?

2) What would be the suggetsed grit sequence for material that has such varying hardness (quartz and lepidolite)?

3) When one is doing several pieces that are say one or a few square inches in random sizes .... what is the best system for separating the pieces so thay do not bump into each other and round the edges? Also, any recommendations for applying weight to the entire group ...or must the individual pieces be weighted. What type of indivisual weights work best?

4) I have some colored tourmaline (elbaite) and beryl slices I would like to lap and bring to a nice polish for use in jewelry .... but will not attempt it without getting some advice .... so same questions as above.

Thanks for your help.

Dennis

From Dennis Durgin - December 11, 2007 at 11:38:42
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Message: 65684

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