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This list digest contains the following message subjects:

1. LapDigest News for Issue No. 26 Monday, 14 Jul 1997
2. RENEW: Polishing Corundum (Was 2-4)
3. RENEW: Tiger-eye Treatment (Was 13-1)
4. RENEW: Orienting Rainbow Obsidian (Was 20-2)
5. NEW: Aussie Opal Cracking


Subject: LapDigest News for Issue No. 26 Monday, 14 Jul 1997

While working on the Index to the Archives, I noted that there were several queries which had been posed but had never been answered. With a larger number of subscribers, it is likely that someone will know the answers to some or most of them. So it's RECYCLE time!!! We recycle 3 of the 5 unanswered queries below; since they are really not NEW, they are now titled RENEW. Can anyone give answers to them?

All items today are either NEW or RENEW ones; there were no responses to past queries. This brings up this point: if we don't have enough items to fill a decent LapDigest issue, it wont go out that day. So if you don't get one some day, start contributing! (smile)


Subject: 2. RENEW: Polishing Corundum (Was 2-4)

I have just cut my first Corundum (Star Sapphire and Star Rudy cabochons). I am happy with the placement of the stars in the cabochons. The problem is I'm not happy with the final polish. This is the hardest material I have cut to date, is there a secret to obtain a high polish? My stages were: 220, 280, 600, 1200, 8000, 14000 & 50000 grit (all diamond). Under water the stones look great.

Do I need to go to 100000, or perhaps I'm just moving too fast through the final stages (but how do I tell?)? Any suggestions would be greatly appreciated. Thank you.


Subject: RENEW: Tiger-eye Treatment (Was 13-1)

I've seen nice catseyes produced from tiger-eye. I understand they use acid to lighten the tigereye to the light honey color. Oxalic acid might be the acid. Is someone familiar with the exact process?


Subject: RENEW: Orienting Rainbow Obsidian (Was 20-2)

I have a large chunk of Rainbow Obsidian rough. I have been told that there is a special technique to cutting Rainbow Obsidian to produce a heat rainbow design instead of a a circular rainbow. It was explained to me once but I have forgotten the directions. Can anyone help with this.
Geri Arms <>

(How about any info on orienting Rainbow Obsidian? -hale)

Date: Tue, 15 Jul 1997 10:28:19 +1000
Subject: NEW: Aussie Opal Cracking

Cracking can be a problem with opal from certain opal fields here in Australia. Minatabie Opal in certain areas can crack badly after only one year. But the miners know what level it is that produces opal which cracks. The opal from that level is very cheap unless you are from overseas sort of thing. The genuine miners there will tell you that it cracks and the majority wil not even sell it to you!!. It simply gives the field a bad name.

It is the overseas buyers who ask for that opal most often, those who have a
large market to sell to and do not care who they hurt. The high grade
stones from Minatabie are just that very high grade and I have never seen
one crack or craze, the same is true with Coober pedy opal.

I love working with Yowah Opal with an Ironstone backing and the opal
intertwined around the ironstone or black Hematite. It produces the most
beautiful of stones and everyone is unique in pattern. (We are mining some
of this material at present if anyone is interested and have some lovely
parcels available between $500 to $9000 US dollars. You can view these on
our web site at )

I have never seen Yowah opal craze or crack unless I have dropped it, which often happens (not using a dop stick). The predominant colors are Green/Blue and Purple. The rarest color in this type of opal is red, and it commands a 5 to 10 fold price increase as a general rule.

But well worth cutting. We cut these stones using only diamond equipment,
otherwise it can chip out from the ironstone; the diamond tends to stop
this from happening. Final finishing wheels, after the 100 diamond, are a 220
nova wheel, then a 1200 nova wheel, then a 14,000 nova wheel. Polish using titainimum oxide on soft felt or 100,000 diamond on leather with a
little oil gives a great finish.

I have a few of the stones cut for you to see on our hand-cut opal web page
if interested. Hope this helps

Cranestone Gems

Tanzanian Gemstone Rough Direct Mine Prices
Australian Opals Rough & Cut At Wholsale Prices
Australian Rough & Cut Sapphires
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