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LAPIDARY ARTS and FACETERS DIGEST
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Issue No. 100 - Thursday April 3, 2003
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Moderated by: Thurmond Moore III
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Committed to carrying on the fine works of
Hale Sweeny and Jerry Dewbre
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POST TO EITHER LINK BELOW:
lapidary@caprock-spur.com
faceters@caprock-spur.com
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VISIT OUR WEBSITE TODAY
http://www.gemcutters.org
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From the Moderator: 

Topical Focus for This Week: Gemstone Photography Clinic


and Dan Clayton submitted this topic:

CUTTING FIRE OPAL

We have post on both subjects today so we will continue
the week with a dual topic. Several more topic suggestions
have come in as well and they will be addressed in the coming
weeks or whenever a topic dies whichever comes first.

NEXT WEEK TOURMALINE CLINIC

Thurmond
====================================
Index to Today's Digest

01  RE:  Stone photography.
02  RE:  Faceting Opal
03  RE:  Stone photography.
04  NEW: photography and dichroism
05  RE: Fire Agate??

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Message:01

Subject: Stone photography.
Date: Wed, 02 Apr 2003 19:59:18 -0500
To: lapidary@caprock-spur.com (LapidaryArtsDigest)
From: "Jonathan L. Rolfe" <webmaster@gearloose.com>

At 06:05 PM 4/2/2003 -0600, you wrote:
>It does not appear that any of the 900+ members takes pictures of their
>stones.


Yes, we do, but for my part I am not proud enough of the pictures to
discuss them!!!  Many on my site are very old, and taken with a camcorder
and a Snappy frame grabber.  I took pictures of them in desperation to
document them for my records, as they were sold and many date back before I
had a web site!  So I had NO IDEA people would ever see them!!!

__________________________________________________________
Message:02

Subject: Another look at faceting precious opal
Date: Wed, 02 Apr 2003 17:06:35 -0800
To: <lapidary@caprock-spur.com>
From: Webb Long <webblong@mindspring.com>

Hi all you happy faceters, If you have  some very  small pieces or chips of
precious opal and would like an outlet for them; I have used quartz  and
glued the opal on what will be the culet, and have turned out some rather
nice stones from what could only be classed as  scrap.     Webb   Long

__________________________________________________________
Message:03

Subject: Re:Digital Gem Photography
Date: Thu, 3 Apr 2003 00:29:18 -0800
To: faceters@caprock-spur.com
From: Phillip L Stonebrook <plstonebrook@juno.com>

Greetings List...

I have just gotten into digital photography myself, and while I am
producing good quality pictures, I give the credit to the camera rather
than my own expertise. You can judge yourself by looking at the following
shots:

http://www.gemcutters.org/showcase/images/ps-005a.jpg

It is a 9 x 11mm Ember cut in light blue CZ, with a finished weight of
8.36cts .. lots of flash and glitter!

Another one, since we're also discussing faceted opal, is a 6 x 7mm
"fine" example of Coober Pedy crystal opal (with the opalescence right on
the crown) in the Cardinal cut, with a finished weight of 1.2 cts.

http://www.gemcutters.org/showcase/images/ps-004a.JPG

I am using a Nikon 950 with it's well known capabilities for macro gem
work. If other list members want a recommendation, I suggest the Nikon
990 or 995, as these models have a better capability that includes a self
timer "while in the macro mode" for more stability and sharper focus.
These models are not the newest and latest offerings from Nikon, so they
can be had thru the "used" marketplace via eBay at a discount from
suggested manufacturer's pricing, usually $300-$500. I understand Nikon's
4500 also is very good, but at higher current pricing of ~$600.

I agree with John McLaughlin's earlier post which directs you to the
following link for great "tips and tricks".
He states "For an innovative, excellent, low cost solution to
photographing faceted work, look at"

        http://www.theimage.com/photography/photopg26.htm

Be sure to browse around on this site, as there is a wealth of
information here. And yes, to give proper credit, it was first posted on
the USFGFacList (original poster unknown - sorry).

Best regards...
Phil in Florida

__________________________________________________________
Message:04

Subject: photography and dichroism
Date: Thu, 03 Apr 2003 13:55:34 +0100
To: "LapidaryArtsDigest" <lapidary@caprock-spur.com>
From: post@maiko.demon.co.uk
Cc: usfgfaceterslist@yahoogroups.com

> photographing large (12 x 10mm) star rubies.

Photographing star stones is very different from photographing faceted stones.  With
faceted stones, you generally need to use diffused light, in order to prevent distracting
"white-out" reflections.  However, if you use diffused light on a star stone, the "rays"
of the star will tend to get blurry, or even disappear.

In order to get the best star effect, it helps to have a single, bright, point source of
light.  To centre the star, it helps if the light is directly overhead - i.e. right next
to your eye or the camera lens.  Unfortunately, this tends to result in unsightly dark
shadows around the base of the stone, and it might not show off the body colour too well.  
Therefore, for the best photos, try combining a single bright light with some additional,
diffuse illumination.  This can be done with little mirrors (you can hold the mirrors in
place with balls of putty or suchlike, so this is a flexible and rapid solution), or extra
lights.  The diffuse illumination should probably be less intense than the single bright
point source, otherwise the star will get blurry.  Incidentally, if you have two or more
bright point sources of light and arrange them in the right way, you'll see two or more
stars.  If you've ever seen a big star stone in a display case under an array of halogen
spotlights, you'll know how crazy this can look!  The single bright point source is used
to bring out the star.  The role of the other light source(s) might be to illuminate the
background, or reduce shadows, or bring out the colour in the stone, etc...  As with all
gem photography, you will need to move the lights around and experiment.

The same goes for cat's-eye stones.  In cat's-eye stones, however, you might also want to
emphasise the "milk-and-honey" effect by only lighting one side of the stone.   See the
following link for more information.
http://www.gia.org/stage/news/ViewIssue.cfm?volume=4&issue=23#4

If you get the "milk-and-honey" effect just right, the cat's-eye look as if half of it is
pale yellow and the other half is brown, with the sharp white line of the 'eye' separating
the two.  This is best done using one main point source, and restrained use of subsidiary
light sources.

If you want to show the "opening and closing" of the eye, I always used to think you
needed two point light sources, and you need to rotate the stone between them.   There's
further information and pictures on the following web link (from Yourgemologist.com, very
useful and interesting site).  However, Robert says on this page that you only need one
light source?
http://www.yourgemologist.com/Colored%20Gemstone%20Grading/GemstoneGradingLesson5.html


Regarding tourmaline:

I have updated my old post on dichroic stones because yesterday I stumbled across a very
nice photograph of a fine dichroic tourmaline which illustrates one of my points very well
(see the last photo).  For those of you who remember this post from last year: sorry to
repeat it, but I thought I was worth updating.  Several of the pictures have been changed
since last time (as has the text), so hopefully you will still find it interesting.

Orienting dichroic stones

Please note that I have linked to various photos that I found on the web.  Most of these
pictures are from commercial sites, and they may have been enhanced beyond recognition!  
However, the photos will at least give you an idea of the point I'm trying to illustrate.

The links are quite long and might get chopped up into two lines. If this happens, you
need to join the two halves back up again before pasting the link into a browser window.

For pleochroic orientation, firstly you need to decide what you want to do. You have three
main possibilities:
1) Emphasising one colour and attempting to eliminate the other(s)
2) Mixing the colours together
3) Contrasting the colours

1) Emphasising one colour rather than the other
If, for example, you have a tourmaline with a nice AB axis and ugly dark c-axis, you will
want to emphasise the attractive colour and minimise the dark colour (N.B. the c-axis is
the long axis of the crystal).
The facets that would normally reflect light in the direction of the poor colour need to
be cut steeply so that they dump light out of the bottom of the stone.

Here's an example of a stone that seems to have been cut with steep end facets. 
Presumably it had a dark C axis colour.  Note that the horizontal lines on the pavilion
seem to extend right up to the ends of the stone - this is a dead giveaway.
http://picture.thaigem.com/pics/smallpic/2h/2h0077600.jpg

N.B. Steep end facets also improve the yield, so don't be surprised if you see this kind
of cut on an aquamarine, for example: in this case, the chosen cutting style has nothing
to do with dichroism.

But here's a tourmaline which wasn't cut with steep end facets.  Note that both ends
appear dark.  Maybe the shape of the rough stone didn't allow for steep end facets?
http://www.multicolour.com/picture/b_ytm230af.jpg


However, if you have a benitoite, then you may have blue in one direction and
near-colourless in
another direction. In this case, you don't have to worry so much about dumping light out
of the
bottom of the stone (because a blue stone with occasional pale flashes is usually OK,
whereas a
green tourmaline with mud-coloured reflections is usually ugly). If this is the case, you
could
try just carefully orienting the rough stone so that when you look down into the table of
the stone, you are looking  in the direction of the attractive colour.
Here's a fun example: a photo of a benitoite that is sitting on a mirror.  As well as
looking into the stone from above, you can see what it looks like from the side.   From
above, it is blue.  From the side, it is almost colourless.  If the cutter had oriented
the stone the wrong way, the colour would have almost disappeared!
http://www.gemhut.com/clipart/ben/ben101.gif

With corundum, you may find that one axis is a nicer colour than the other.  Some
Australian sapphires are blue on one axis and an ugly green on the other.  I've read that
the typical, fat-bellied "mass-production cut" (or "native-cut", for those of you without
the Faceting Political Correctness Dictionary, 2003 edition) is good for emphasising the
face-up colour.  The steep sides of the "belly" apparently minimise the amount of light
going across the stone: most of it goes straight down deep into the stone (in the blue
direction), only a short distance across the shallow pavilion facets (in the green
direction) and then straight back up again.


2) Sometimes you want to mix the two colours together (for example, because you want to
maximise the yield and you can't afford to emphasise one colour, or because the two
colours complement each other). A round brilliant cut or a barion will do this, if you
align the stone right.

Here's an example of a tourmaline cut by Jeff Graham. It is apparently dichroic
(blue-green on one axis and yellow-green on the other). You can see that the colour is a
mix, but there are flashes of blue-green and yellow-green.
http://www.faceters.com/gemstones/images/rbgraf.jpg

Jeff has a very good web page with advice on dichroic stones (amongst other things). Check
out
http://www.faceters.com/askjeff
.particularly the following page:
http://www.faceters.com/askjeff/answer51.shtml

When the dichroic colours are mixed in a stone, to the untrained eye it sort of looks a
bit like dispersion.  It's not unattractive.
http://www.multicolour.com/picture/b_ytz163jj.jpg

However, you may find that the flashes of the two separate colours can concentrate in
different areas of the stone. This is especially true of non-round cuts. For example, if
you cut a pear, light sometimes gets "funnelled" into the tip, so you may find that the
tip is more one colour and
the rounded part is another.  This can look a bit strange.
http://www.multicolour.com/picture/b_ytz162be.jpg

You may also notice that one colour overpowers the other (e.g. in iolites, if you orient
the stone in the blue direction, the blue colour will tend to wash out the near-colourless
and yellowish colours, so there isn't much point in trying to mix the two: usually it's
best to just maximise the blue).  In general, darker shades overpower pale shades.   If you
cut an iolite with the blue direction facing up through the table, you will probably not
be able to notice any flashes of the pale yellow or colourless colours.


3) Providing a contrasting display
This is something that isn't talked about much, but it is important. For example, the
whole point about andalusites is that they have nice contrasting dichroism between the
pinkish and the green.  If you want to provide a contrasting display, then cutting a round
brilliant is usually not the
best thing, because it has complex reflections and the two colours might mix too much
(e.g. you might just get brown, instead of a contrast between pink and green).

Here's an andalusite which, in my opinion, has the colours mixed together a bit too much.
http://www.gemcutter.com/gems/acfpr/r618.jpg

If you cut a more asymmetrical shape, like an oval or marquise, then you might get better
results - e.g. an oval with a green "bow-tie" centre and the pinkish colour concentrated
in the two ends:
http://www.multicolour.com/picture/b_yad006e.jpg

However, it's not enough just to cut an asymmetrical shape. You also have to align the
stone so that the colour goes in the correct direction through the stone. Contrast the
previous photo with the following one and you'll see what I mean.  The red colour
direction seems to be going from 2-o'clock to 8-o'clock, instead of from 9 to 3.
http://www.multicolour.com/picture/b_yad005as.jpg

An emerald-cut can also be very good for this kind of contrasting colour display, because
the facets are aligned in two very distinct directions, so they can "aim" the light very
well down the different colour directions (unlike an oval, where you will get a bit more
mixing going on).

Here is the very nice tourmaline that I was talking about. It is blue on the ab axis and
green on the c-axis, and has been cut very nicely (concave-cut pavilion?) to show the blue
colour in the centre blending in to the green on the ends.  Very nice!
http://www.professionaljeweler.com/pjicons/archives/oct98/1098gn5.jpg

Incidentally, I've heard this type of dichroic stone referred to as "double-sided"
tourmaline.  Quite a bit of it came out of East Africa recently.  Some of the East African
material has a very nice pink on the C axis and an orangy colour on the AB axes.  If you
aren't careful, these will mix together and make brown.  It's probably not a good idea to
attempt to cut such a stone in the same style as the tourmaline you've just seen, because
the colours don't complement each other so well.  "Blue -> teal -> green" is much more
attractive than "orange -> brown -> pink".  Maybe try a plain emerald-cut instead, which
doesn't mix the colours so much.

Note that with some dichroic stones, you might simply find that either one shade
overpowers the other or that the two shades mix together, no matter what you do.   This is
probably due to human colour perception.  So I suppose the cardinal rule is to be careful
what you buy!  If you buy dichroic rough, ensure that the two colours either complement
each other, or provide a nice contrast, or that the shape of the rough is such that you
can orient the stone in the direction that you want.  Hopefully, seeing these examples
will give you an idea of what can be done with dichroic rough if you are careful, and what
might happen if you're unlucky!

?8-)
-Michael.

__________________________________________________________
Message:05

Subject: Fire Agate??
Date: Wed, 2 Apr 2003 23:47:29 -0600
From: "Pauly Sanders" <redhog@midwest.net>
To: <lapidary@caprock-spur.com>


Hi Thurmond,
You wrote:
>The same thinking applies
to fire agate as well.

I'm finally getting around to trying to something with the 5lb or so of
fire agate I dug at the Opal Hill mine in CA over a year ago. Not
knowing anything about it a threw a handful in a tumbler to see if it
would remove the matrix and let me see if there was any fire.  It seemed
to work pretty well removing the softer rhyolite and not damaging the
agate.  So, I did several more barrels. So far I've found two pieces
that look very promising.  Now I need info about how to proceed with
bringing up colors/fire. It sounded like you may have worked with it.
Any advice??

Regards,

Pauly Sanders
Sanders Gemology Labs
Herrin,IL

_______

Hi Pauly,  I have never actually cut Fire Agate but have read about it on Hale's
Lapidary Digest Site as well as other sources that escape memory at present.
Also there are several "old timers" in our club who have cut it who have issued
very stern warnings that it can be ruined by overcutting literally in the blink of the
eye. I am sure that someone on the list has cut it and should be able to provide
additional insight.   Anyone game??

Thurmond
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Lurking is fine, but participation is better for learning !
Post something from your experiences in gemcutting today!
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TODAY'S FUNNY ~

Thoughts and stories from on the job

My boss came in one morning and caught me
hugging my secretary. He said in a rage, "Is this
what you get paid for ?" I told him, "Nope ! I do
this for free."

This same boss was into all this dumb inspirational
and motivation stuff too. I remember once he
posted a sign which read "Today is the tomorrow
you worried about yesterday." I couldn't resist and
added a note: "And now you know why too".

Once I came upon this pretty new temp standing
in front of the paper shredder with a confused look
on her face. I asked if she needed any help and
she said, "Yeah, how does this thing work ?" I
took the papers from her hand and demonstrated
how to work the shredder. She stood there a moment
with yet another confused expression, so I said, "Any
questions ?" She said, "Yeah, exactly where do the
copies come out from ?"

People always say that hard work never killed anybody.
Oh yeah ??? When's the last time ya ever heard of
anyone who "rested to death".

Being punctual in our Office was of no benefit what-so-ever.
There was never anybody around to appreciate it.

Our Office was always on the cutting edge of technology.
Not only did we have computers which spoke as well as
listened; some of them even got ulcers.

Did ya ever notice the people who complain the most
about not having enough time to do all their work are
the same ones who always stop & tell everyone that
they don't have enuff time to do all their work.


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REFLECTIONS AND TIDBITS:

To belittle is to be little.

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