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 Post subject: expanding the collection; our first goshenite
PostPosted: Tue Mar 11, 2008 8:39 pm 
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A little less than year ago we (only just) managed to get ourselves to the O'briens creek topaz fields in northern Queensland, Australia. A week earlier a friend of ours, seargant Stan from the dutch Armed Forces had come over to visit us and have a sniff of digging for gemstones. We wanted to check the spot out anyway so off we went in our Landcruiser army ambulance.

We travelled there from Mareeba, some 200 km to the north-east of the fields. Taking the shortcut-backroad we passed some beautifull remote part of the area. Our friend spotted his first, live, wallabies and we enjoyed the trip chatting, drinking beers (my better half was driving, don't you worry) and just being stupid. At 5 km before arrival the driver all of a sudden called out: "I have no clutch!"

Three weeks earlier my gearbox had died so we replaced that one and had a look at the clutchplate; it was still fine. But sure enough, one of the rubbers in the clutchcylinder decided to go to rubberheaven. "good thing that didn't happen 100 km ago" our seargant said. I asked him what he would do in such a situation when at work. "call the technical staff" he replied dry. Well that wasn't really one of our options there and then so we just crashed it in first, got it going and then crashed it in second when we gained some speed. Positive thinkers as we are we just continued drinking beers and being stupid while going at a steady pace.

We'd promised the seargant real bushcamping in the middle of nowhere as we'd done the entire previous year and he was keen to show us his survival skills. The clutch problem would be dealt with in the morning, priority was to get ourselves to the designated campground where, we were told, a caretaker would be present. Upon getting the campground in sight the laughing stopped and our mouths fell open. There was at least 300 people camped there!! Easter weekend! Stupid me hadn't thought of that. It seemed like the whole of North Queensland had decided to go out for a dirty weekend of fossicking.

So much for pristine bushlife. But ah well, at least somebody would be able to get me into civilization the next day to get some parts. We set up camp at the end of a row of tents and campers and went to sleep.
The next day I learned that there would be no way that I would be able to get new parts in Mount Surprise, 15 km away, and that my best bet would be Mount Garnet (don't you just love all these names?) some 150 km away. Woops... Anybody going there in a hurry? Some fella was, two days later, to pick up his wife and then come back. He offered to bring a whole new cylinder with him. Perfect! So much for the worrying, lets start digging!

The actual field was another 6 k away but hey, seargants can walk 6 k, can't they? So there we went, marching towards the topaz. After half an hour it became obvious that the fighting spirit of dutch seargants is kind of temperature related. A big red head was looking over his shoulder to see if there was any cars coming to give us a ride and asking how much ground we covered yet every 100 meters. Suddenly, appearing when we walked over a crest, some large black thing was sitting on the road. A 2 meter monitor lizard was having a sunbath. Right up my missus' lane, these kind of situations. She lives by the rule: if you have a camera in front of your face then nothing can happen to you. I've seen her walking right up towards a tiger snake once just to get a better picture. I get goosebumps just writing about 'm. So off she goes like seeing a sweet little puppy. While she's taking her pictures the long awaited car that could give us a ride comes screaming over the crest. Seeing us and the dino he hits the brakes and gets out. After chasing the suicidal lizard off into the safety of the scrub with a long rope he offeres us a ride to O'brians creek. The seargant was on the back of that ute faster then any tiger snake can strike.

We dug up 6 pieces of topaz that day, a lousy accomplishment after hearing my mate's story of getting over a 1000ct each day. The next day didn't prove to be any better. When our angel came back with the cylinder parts yet another day later I set to get the car working again and realized soon: this is the wrong parts... After 3 days of fumbling around and a lot of well meant bogus advise of all our fellow campers I finally was able to make three parts into one and it kinda did the job. We decided to get ourselves back into civilisation while the car was running.

My girlfriend, who is a cutter, refused to leave without a fair amount of cuttable topaz so she started asking around if she could buy any of somebody. One lady answered with the words, "we don't sell rock", and gave her two hands full a second later. As you can imagine: one happy girlfriend. One of the pieces was a bit light for topaz and the donator told us it was colourless beryl. Having read that goshenite and aquamarine aren't uncommon there we took that for granted, the lady had been digging there for 50 years, surely she knows her stones.

Last week that piece of rock ended up on a dopstick in Holland. It was cut to a 10ct modified emerald cut and was our first cut goshenite. I even checked gemval for an idea of value: $285,-. Nice gift I thought.
About an hour ago I pulled it out of the methylated spirits container to remove the final bits of glue. As far as colourless stones with low RI and little dispersion can be pretty this one can be called just that: pretty.
I always chuck new stones through the usual tests just to practise. So why not this time?

SG: (always rough with my 0,01 g accurate scale) was 2.69. "Yep the lady was right," I thought.

Just to practise lets get a RI: 1.549-1.552ish. Ehm... that's strange...

Polariscope and sphere where in front of me in a flash:
and what the ....! : Biggest bulls-eye possible...

Oh my goshenite!


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PostPosted: Wed Mar 12, 2008 12:17 am 
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Great story Spauwe. Good luck on the next mission.
Cheers

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PostPosted: Wed Mar 12, 2008 12:25 am 
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Great story, Tim, I enjoyed that immensely! :lol:

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 Post subject: Re: expanding the collection; our first goshenite
PostPosted: Tue Jun 07, 2011 11:49 pm 
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Hi Tim
Great story which I enjoyed. Any more?

I am sorry to disallusion you but the RI measurements of your supposed goshenite (colorless beryl) given as 1.549 to 1.552 are those of quartz, not beryl, which is 1.57 and above.
You say that you tested the cut stone with a polariscope and got some image but didnt say what it was.
If you get an optic axial image, then quartz shows an uniaxial + one with concentric rainbow colors in the centre of the black cross. This is different from the beryl optic axial image which is uniaxial negative and the black cross meets in the middle.
Also, by careful observation of the RI shadow edges you can theoretically tell whether O is greater than E-ray, or viceversa.
Try it out again and lets know the result.
Cheers
Allano


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 Post subject: Re: expanding the collection; our first goshenite
PostPosted: Wed Jun 08, 2011 3:44 am 
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I'm glad you enjoyed that story Allano. :D There is a few more of those floating around the board. Search for 'Frankie goes to Rubyvale' and 'Zircon Valley'.

In reaction to your well meant remarks:

Among us gemologists we call the interference figure seen in Quartz a 'Bull's Eye'...

Image


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 Post subject: Re: expanding the collection; our first goshenite
PostPosted: Wed Jun 08, 2011 4:49 am 
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Hi Tim
Thank goodness for that! You had me fooled.

May be the average reader of your post will not understand the subtle nature of your message?

Perhaps its a good idea for a gem cutter to examine the rough material with a polariscope and try and determine the optical orientation (plus other properties) before preforming.

Can't say I ever did when I faceted gemstones a 100 years ago, but then all that was available was the tiny Rutland polariscope, not the present models where you can manipulate easily a faceted or rough stone and hopefully get an optic axial image.

We (at least I do ) learn something every day.
Glad you enjoyed your visit to Australia.
Cheers
Allano


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 Post subject: Re: expanding the collection; our first goshenite
PostPosted: Wed Jun 08, 2011 4:56 am 
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Quote:
May be the average reader of your post will not understand the subtle nature of your message?


That's alright... we ought to be able to have a little fun amongst ourselves :wink:

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Perhaps its a good idea for a gem cutter to examine the rough material with a polariscope and try and determine the optical orientation (plus other properties) before preforming.


Not possible unfortunately... no polish -> no figure... You could determine the optic axis (the isotropic direction in anisotropic, uniaxial materials) with a polariscope by approximation but usually the irregular outside of rough will make that a difficult task.


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 Post subject: Re: expanding the collection; our first goshenite
PostPosted: Wed Jun 08, 2011 5:05 am 
allanotaylor wrote:
Hi Tim

.......Also, by careful observation of the RI shadow edges you can theoretically tell whether O is greater than E-ray, or viceversa.


'Theoretically'? I find it very practical. i'll take it over the 'this year, next year, sometime, never!' use of a conoscope, any day of the week :lol:

Tim wrote:
.....I'm glad you enjoyed that story Allano. There is a few more of those floating around the board.


Nice one Tim. Irony from a Dutchman. Whatever next! :lol:


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 Post subject: Re: expanding the collection; our first goshenite
PostPosted: Wed Jun 08, 2011 10:31 am 
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Quartz has been used as an impressive impostor for tons of things over the years.

Si Frazier did a report on the quartz which has been identified as diamond in jewelry made over the centuries for the Sinkankas Diamond Symposium.

I'm glad Allanotaylor found this old thread. It's a really good one!


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