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Techniques for CollectorsQuartz Wedge

22nd Apr 2012 22:00 UTCDon Saathoff Expert

I'm STILL looking for a quartz wedge that I can afford - a new one is WAY out of my price range. A three- or four-order wedge would be wonderful. Even trade would be great!! We have several large old slabs of Kelly smithsonite, many unknowns REE minerals from the Rode pegmatite in Llano, TX. Just to name a couple of things.....

The 'scope is a Zeiss student model and takes a standard DIN plate..

HELP!!!

Don

22nd Apr 2012 23:00 UTCHenry Barwood

Don,

There is a short description of how to make optical wedges out of stretched acrylic plastic in:

Am. Min. 67:853 1982

Taggart, K. C.

Inexpensive "Quartz Wedges"

Might take a few tries, but would certainly be cheaper than a real quartz wedge.

23rd Apr 2012 00:47 UTCDon Saathoff Expert

Thanks Henry, I read that article some time ago but decided to try for quartz again.....if no luck, I'll probably try the acrylic....

Don

24th Apr 2012 14:37 UTCDonald Peck

Don, when I was cutting thinsections free hand, most of the time they wedged out on me. I wonder if one could intentionally cut a wedge from quartz, and if it would be useful?

24th Apr 2012 18:05 UTCDon Saathoff Expert

In our local club there is a gentleman who is a faceter. He has offered to try and I will probably take him up on his offer. I have the dimensions required for a 4-order wedge but haven't decided on a substrate yet. I'll try a good quality microscope slide.

The difficulty with the acryllic is the optical quality - it would have to be used on the stage....

And, yes, hand-lapping a thin section is an art I haven't mastered either!!!!

Don

24th Apr 2012 22:04 UTCOwen Lewis

Don,

Try Hyxtal (http://www.hxtal.co.uk/) its the epoxy of choice for those skilled jewelers who make composite gems. A chat with them may help you settle the grade you want for this application.

24th Apr 2012 22:32 UTCCharles Creekmur Expert

Don,

Some years ago I made a wedge. I had a large block of clear quartz that I cut a oriented slab out of and went to one of our local club faceters and had him grind it for me on my direction. It turned out perfect 4 orders but I suspect that was 1 % "knowing what I was doing" and 99% "beginners luck". As I remember, I used Canada Balsam on a regular microscope slide.

Good luck,

Charles

25th Apr 2012 00:30 UTCDon Saathoff Expert

Thanks All!! Another Mindater has a spare & and is willing to part with it!! It should be fine for my needs..

Don

26th Apr 2012 16:11 UTCDonald Peck

I have a 4-order quartz wedge that was unmounted. I mounted it on a microscope slide with Canada balsam and it works fine. I have toyed with the idea of mounting it by its edges in a carrier and having no substrate but have not tried it. I would worry a bit about the brittleness of the thin end.

26th Apr 2012 17:49 UTCDon Saathoff Expert

Don, I believe even those wedges mounted in a carrier are on a substrate. When I was contemplating construction I found a site with an "exploded" view of a wedge and it showed a substrate onto which the wedge was attached w/ balsam. I was going to use a sandwich of hardwood.....

Don

26th Apr 2012 21:58 UTCGary Moldovany

Please forgive my ignorance, but I have no idea what a quartz wedge is or what it is used for. Would someone be kind enough to enlighten me? Thanks! Gary

27th Apr 2012 00:00 UTCDon Saathoff Expert

Hello Gary,

When studying the optical characteristics of a non-opaque mineral with a polarizing microscope there are two accessory plates used to aid in determining optical sign (+/-)....among other things. One is the Gypsum Plate which has a fixed retardation and the other is the Quartz Wedge which has a "variable" retardation.

For a better explanation Google "Optical Mineralogy"......there is no quick & easy way to describe it's use....(sorry!!)

Don S.

27th Apr 2012 16:10 UTCDonald Peck

Don, When I mounted my wedge, I cut Lucite for the carrier. I cut a recess in the edges of the opening so the piece of glass slide with the wedge rests in the dadoed edges. Works fine.

27th Apr 2012 19:43 UTCDon Saathoff Expert

That would work...

16th Jun 2012 03:06 UTCGerald Wells

I have a quartz wedge that I made many years ago. It is mounted on a slide and I have used it many times for gemology. If someone is interested I can look it up and send some measurements and pictures. I switched to another interest and haven't used it for a while.

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