Hello all.
I have acquired a nice slab of Labradorite and there are two
distinct places that have “the play of color.” I am having trouble
orienting the stone so as to get that “play of color” when the stone
is shaped and that one can see the play when looking at it.
How do I find the right angle?
Thanks in advance for your help.
Stephen
Fortunate timing. I just put this in our club newsletter - Debby
ORIENTING OBSIDIAN, LABRADORITE AND SPECTROLITE
Jim Small. Small Wonders Lapidary
Obsidian:
Orienting Obsidian depends on what type of obsidian and what you are
doing with it. If you are polishing flats. the best way to orient
rainbow sheen obsidian is 10-15 degrees off the plane of the parallel
bands. If you are cabbing it, cut exactly parallel to the bands. Sold
sheen is always cut parallel to the bands or the effect is lost or
diminished. Fire obsidian sometimes loses its fire sheen when cut
parallel and should be cut after careful examination of the best
angles for viewing the fire which is actually in between bands. Other
types of obsidian look different when cut at different angles to the
bands; midnite lace is one such example, where you should experiment
until you find the “look” that pleases you.
Labradorite/‘spectrolite’:
Here is a procedure for orienting labradorite/spectrolite. It will
also do a credible job with moonstone. With most sunstone (India and
upstate NY) orientation is simpler because you will just orient for
the schiller (metallic flecks).
Set a student desk lamp; what we used to call a high-intensity
lamp. They usually have a switch for two brightnesses. and they
always have clear glass bulbs (this is important).
Fix a high shelf where you can put your lamp. so that you can
adjust the arm to have the beam of light shine straight down onto a
flat surface which needs to be no higher than thigh-high. A stool or
flat-top crate will work fine.
Set a tin, like one of the tins which Danish butter cookies come
in; it should be anywhere from 8" or “>” in diameter up to 12" in
diameter. and between 2" and 3" deep. Fill this tin about 3/4 full
with sand or fresh kitty-litter or any other finely granular
material.
Set a really good quality water-proof marker. It should be at
least 6" long. and ought to have a relatively fine (no more than
1/8") point. Round-nose markers work fine as long as they haven’t
been squished by pressing too hard.
Stand on the opposite side of the stool/crate from the shelf with
the lamp. /Adjust your stance and the lamp so that you can look
straight down on the middle of the tin while the lamp shines its beam
straight down above the top of your head. without your head occluding
the beam.
Place a piece of mono-crystalline labradorite in-the granular
material-in the tin. so that at least 2/3 of it is above the
supporting grains. If you have polycrystalline pieces of labradorite
you either have to cut them apart along the crystal boundaries. or go
for the largest or showiest crystal, and trash the others.
Slowly rotate the labradorite until you see a flash of color;
once you locate a flash slowly spin the piece until you have the very
brightest flash showing right on top. After you have the brightest
surface centered rest your permanent marker on the top edge of the
tin. and drag it slowly around the piece. leaving a mark all of the
way around. This mark should be parallel to the top flash.
Slice your crystal parallel to the mark to cut slabs which will
produce finished cabs with a broad color flash over their top
surface.
Some labradorite will behave like moonstone. and have the capability
of producing a floating eye in a cut cab. To test whether your stone
has this capability take the following additional steps.
Place the stone on its side. so that the marker line is straight
up toward your eye. Slowly rotate the stone. keeping the line in
vertical orientation. When you see "another flash (it will be
distinctly weaker than the broad flash which you already marked),
test its location by slowly revolving the stone from left to right or
vice versa until you have the best flash firmly centered on the top
of the stone. It should be somewhere on the first line; if it isn’t,
start over from the beginning.
After the second flash is firmly centered. draw another line in
the same fashion as the first one. The two lines will not meet at a
90 degree angle. but nearly so.
Slice the crystal parallel to the second line to produce a
floating eye in your finished stone.
Now. to make things really interesting. there is some labradorite
from Labrador that not only has labradorescence. but it also has
schiller. In effect, it is labradorite/ sunstone. If you have any of
this material you will see the small metallic flecks show up when you
do the first orientation. If you have this material. don’t bother to
look for the floating eye because the schiller is much rarer as an
optical phenomenon.
You can get into really fancy tricks with the orientation if you
want to. like having pendant stones that flash only when they are
hanging on someone. Labradorite is not recommended as a ring stone,
nor a bracelet stone: it is much too soft and tender for anything
that rugged. Also, since it is a feldspar it has perfect cleavage in
two directions; a sharp rap will cleave it!
From The Glacial Drifter: 50(8):5 November 2007 via GEM CUTTERS NEWS
11-06
Hi Stephen,
Hold the piece with your head blocking any direct light. Rock it back
and forth until you see maximum color. The back of the cabochon (or
table of the faceted stone) needs to be located perpendicular to the
direction in which you are looking. Flatter cabs will work best; a
highe dome will tend to restrict the directions in which good color
is visible.
Because the phenomenon that creates the color is planar, the color
will always a ppear as a “flash” as opposed to having a constant
presence as the stone (finished or unfinished) is moved.
Hope that helps.
Wayne Emery
thelittlecameras.com
when i have a problem like this one orienting a cabochon lets say,in
a pendant, i put the color play in the piece of jewelry at a position
similar to that which it will be in when its on the potential wearer
(you are going to have to guesstimate). somtimes i find that if i
recut the back of the cab at a differebt angle relative to the top it
fixes the "facing up " issue. you need to analyse the color play area
in relation to the position the stone will be in for the finished
piece. i think this is called orientation and it is key in having a
stone of value, anyhow i cant see the rock so, this is the best
advise i can give blind or visually uninformed, take a chance, make
the mistake! then fix it. thats the knowelege money can’t buy - goo
I will try as best I can to answer that question, but as I cannot
see the stone (slab) in question this may not be precise. First,
although this part will deal with unsawed rough I think it may help.
I will add some notes at the end that may address your concerns. In
any event this (first part) is what I wrote to the IGS some years
back on how to orient the rough, to wit:
Dear Sir;
I noticed that no one wrote in about orienting Labadorite, perhaps
you can pass this along, although I feel like this is not far removed
from the adage about the blind leading the blind perhaps it will
help.
Orienting Labadorite
Perhaps I should not reply as you probably have been given this
remark on the orientation of Laborite. Moreover I know very little. I
attended a rock show in Ogden and while there I bought one chunk of
this stone to play with. The guy that sold me this told me that the
most important thing with this stone when cutting it is the
orientation.
To do this get your rough wet and turn it until you get a good slash
of color, mark this, it will be the “top.” You will want to then saw
the rock in layers so that this color will be flat across each slab
cut. If you get more than one splash choose the strongest, I doubt
any grinding will be needed to see this color. When I bought mine I
picked out a chunk from others that were in a bucket of water and all
despite irregular shapes an area to be marked as a starting point was
clear.
Otherwise without orienting you will get a translucent gray stone
without the desired color splash.
I also noticed something else and I do not know if this is usual
with this material, or if it was just with the piece I bought. That
is, on the slab there was a stripe or zone so to speak of color flash
about 1-1/2" across while the optical properties on the other side of
this were different so I used masking tape to mark this break before
cutting it along that line. (This divide was on a healed fracture.)
When the finished cab is turned you will want the color flash across
the whole stone. So if you see this in a slab you cut to the divide
(two, instead of one big stone). This way you will be more pleased
with the results.
The fist cab I cut I did not do this above step and instead cut one
large cab. The results were a bit disappointing as often, one half
only would flash color, the other half would be a translucent gray,
and vice versa. Again I do not know if this zone is usual, at least
with that variety or not. But this zone is something to notice if
present, as I believe that usually you would want the whole cab to
flash (always). As said I know very little about this and was hoping
that someone else would write in, as I too could use some tips and
tricks on this material.
Spectrolite vs. Labadorite
Although the names Spectrolite and Labadorite are used
interchangeably this is not correct. Spectrolite is Labadorite; most
Labadorite is not Spectrolite.
Spectrolite was found in 1940 during World War II when the Finns
built a defense line on the eastern border. “Spectrolite is regarded
by gemologists as the world’s most beautiful labradorite,” it is
said. (This is also reflected in the price you will pay for it.) As
each country is entitled to name its own Professor Aarne
Laitakari, then Director of the Geological Survey of Finland chose
the name “Spectrolite.” Spectrolite is a labradorite feldspar, a
member of the albite-anorthite series with about 55% anorthite.
If the composition is different then it is another variety (some
other names are also used, but there are different varieties with
differing properties, although I can not comment on any of those,
technically these are different. I, as said, bought it to play with
not knowing what to really expect.) The other I learned
later after seeing what this is and concluding that I want some more
of it.
From a web site we have this bit of interesting “If cut
to a normal-domed cab, the Ylaama material that we have (maybe others
as well) displays a sharp and straight cat’s-eye over the
labradorescense… I like the flat-topped cabs we produce better
though; the eye is not as evident, but the play of color is
stronger.” (I can say the material I got will not cats-eye, but then
again it cost a lot less than the Ylamaa material. Although I have
one cab that is very, very nice.)
I know this is not much help. However I am very surprised that
someone with a lot more experience with this material did not reply
to your question. All I can say is that it is not hard to cut and if
oriented will produce some nice stones.
NOTES:
I cannot see the stone, in my hand, for that has been my greatest
teacher, i.e. some mistakes, then you know what works (or not).
(Every stone is different.) However I must assume two things, for
purpose of this instruction. First is that the slab was correctly
oriented (sawed). Second is that you want a pendant. Labradorite is
Very light directional, that is if great color is in one direction,
if turned upside down it is the opposite. Now take that slab and
turn it every way, with the light coming from above, then mark that.
This will be the top of that cab when cut, hope this helps somewhat.