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Working with labradorite


#1

I have read on a web site that Labradorite is difficult to work with
from a jeweller’s perspective. I have found a deposit of Labradorite
here in BC and I am wondering what the problem is in crafting or
carving it. Does anyone have experience working with this stone?

PtP


#2

PtP…I have long worked with Labradorite and, personally, I enjoy
the stone. It does require some effort to achieve proper orientation
and that may scare some lapidarys away. Similarly, many don’t care to
go through the fuss of properly orienting tiger eye or amazonite,
etc.

Much of the problem is caused by poor orientation during the
slabbing process. If the slabber does not properly slab the stone, it
is often impossible for the stone cutter to find the proper plane of
color.

But, if properly slabbed and cut as a gemstone, the ‘jeweler’ should
have no problem setting the stone.

Good luck with your find and cheers from Don at The Charles Belle
Studio in SOFL where simple elegance IS fine jewelry!


#3

Once you slab a section of the material, take it out into good
sunlight and bring a soapstone or graphite pencil with you, turn the
piect and find the surface that gives you the most chatoyancy and
spectrum of colours. Mark it off. Using a diamond saw blade ( or any
thing you prefer) rough out the forms you want to use in your
jewelry ( the diamond sawblade can go right into a jeweler’s hand saw
and with a bit of bees wax or bur lube on it slices right through the
material- a dremel with a diamond wheel works equally well as any
flex shaft with the same diamond wheel/saw if the slab is no more
than 1/2 an inch wide, or if you have lapidary equipment this is the
time to use it. THe material is not hard at all to work with. You may
first go to a stone countertop dealer as many of them are using
labradorite for counters, and get some scrap pieces to work with
before mining it yourself from the deposit you’ve located. The good
thing about trying your skills with scrap is that it will have at
least 2 flat sides and possibly one polished already, making it
easier to see the orientation of the subsequent cuts you should make
to get the best play of light in the material. I have probably a ton
of labradorite in various colours and forms ( spectrolite, swedish
labradorite, green, etc.) and I have found it very easy to work
with as long as you have decent saw blades and supply of polishing
compounds to work it to a reflective shine when it is cabbed.

RER


#4

The constant with labradorite is the need to orient the stone
correctly. It is a feldspar, composed of many thin layers stacked one
on the other. You must cut dead parallel to the layers in order to
get the play of color or labradorescence showing to full advantage.

Depending on the rough, you may also have to deal with crud spots in
the material and delamination of the layers.

Other than that, not difficult to cut.

Lee


#5

PtP,

Labradorite also has some other characteristics that need to be taken
into consideration. One, incipient cleavage (Those basically parallel
lines you’ll see in a slab or polished stone) and it’s propensity for
natural fractures. Another factor that needs to be considered is
whether or not the flash is essentially visible over relatively large
areas over a properly oriented slab or do the flashes occur in small
areas, or when the slab is tilted at various angles. Color and
combinations of color are important too, as is the field color. Other
than the extra care needed to properly orient the stone as Coralnut
stated most Labradorite is cut low-dome to bring out the greatest
amount of flash. Another factor to remember is that a cutter
generally wants to cut the stones a little thicker- too thin and
those incipient cleavage lines can wreak havoc when you try to set
the stones.

Also, is the Labradorite you’re finding translucent when slabbed or
is the stone essentially black and opaque? If it is black and opaque
with multiple color flash you may have discovered another source of
Spectrolite, which generally commands a higher price.

All in all though, again as Coralnut stated, it is a pleasurable- and
absolutely gorgeous- stone to work with.

Kenton


#6

Are you speaking of faceting quality or cabbing quality material? If
cabbing, the labradorescence is directional within each individual
crystal, meaning that to develop the material as a gem you are
obliged to orient it correctly. As most masses of labradorite are
polycrystalline this means either breaking/sawing the mass into
individual crystal sections, or sacrificing much of the potential to
develop the beauty of a major exposed crystal. Properly orienting
labradorite is complicated by the fact that, as a feldspar, it has
perfect cleavage in two directions. Much (perhaps most these days)
labradorite is damaged by blasting during the mining process; the
blasting creates internal damage within the body of the mineral which
results in the crumbling of the crystals along cleavage planes.
Hand-mining minimizes these problems.

Jim Small
Small Wonders Lapidary
Church Hill, TN


#7

Peter asked about working with labradorite, especially crafting or
carving with it. I assume that the grayish form with the strong play
of color is being referred to.

I have made a few small oval cabochons of labradorite from the type
locality in Labrador. Material from there tends to be fractured,
also it is similar to other feldspars in that it is brittle and
somewhat soft. That makes it difficult to find large pieces without
flaws. Other than that, labradorite is easy to shape into typical
cabochon contours and polishes readily with cerium oxide. I have
carved quartz and lapis lazuli, and I could imagine that a piece of
labradorite solid enough to hold together as a cabochon would perform
just fine as carving material. One thing, though: cabochons in
labradorite are usually oriented for best color, and the color flash
is best in a relatively flat stone. A carving would probably not show
the butterfly wing flash well unless its design were relatively flat.

I’m not sure what the term “crafting” means. If it means using it
for inlay or beads, labradorite with a strong play of color would
probably work, but I have not done either. Maybe someone else can
provide some insight.

Dick Davies
Cutter


#8

Labradorite shows a play of light called schillerescence in a plane
only a few degrees away from its cleavage plane which means it is
susceptible to chipping and cracking if you are too rough when
cutting and grinding it. It is softer than quartzes so fairly easy to
work but avoid coarse grained abrasives. Anyone who has cut cats eye
stones or opals before will have no trouble cutting it, freeform
cabochons lend themselves well to this stone and allow the cutter to
make best use of the material. It will lend itself well to carving, I
have seen some very good pieces so there are people about who
understand it. I met a man from Pakistan last weekend who did some
lovely work, I wish I had taken his details. I can ask the show
organiser for them to forward if you want.

Nick


#9

Thank you for the helpful feedback, Kenton; also to others who
responded as I made notes from all of the postings.

I have found samples from two outcroppings now, about 300 feet apart
in elevation on the mountain with lots of overburden in between.
Certainly these samples are interesting from a geology perspective
but I have little idea if they also have lapidary/jewelry interest so
I’ll expand some more.

I am not sure yet if the outcroppings are closer to original
sedimentary or igneous deposits. The geological maps say the overall
formation is Jurassic (the end of the dinosaur age) but they describe
both sedimentary and volcanic rocks in the outcroppings so it is more
complex than a single time of formation. Volcanic andesite carries
much feldspar. Repeated periods of volcanic activity could also
transform the original lavas or the sediments derived from them.

The host rock is coal black but it is highly fractured. Some
geologists think this region has seen a major earthquake about every
500 years. The fracturing seems to leave some rock faces exposed to
weathering and these turn a dark, rusty brown. I have seen a number
of
Labradorite samples on web sites and those with the lighter
background rock seem to yield more obvious iridescence so the darker
background probably detracts from the aesthetics. It is only on the
weathered faces that the iridescence appears and it is lost when you
make a rough cut with a geologist’s hammer into the black host rock.
I don’t have the equipment to do slab cuts.

So far my hunch/theory is that the weathered feldpar is transformed
by later periods of nearby volcanic activity which glaze these
surfaces and produce all the colours of the rainbow but (as sampled
so far) only on the weathered surfaces so whatever the chemical
transformation on those surfaces it seems necessary for the
colouring. Red, orange, yellow, green, blue, indigo and violet are
all apparent so far. Some samples display a few colours and others
display a different part of the spectrum but all are in the deposit.
The greens and blues are especially impressive because I have never
seen such vivid colours before in my prospecting trips. They look
like marine enamel paint has been dobbed on the rock. That is, they
are deep or saturated colours. Green is as common as the other
colours except blue which seems to be the rarest. The uni-colour
"spotches" are typically 1-2 mm in diameter. My hunch/theory is that
the black host rock is andesite-like with a high feldpar content. The
original lava was eroded and became a high feldspar content
sedimentary rock. Subsequent volcanism then glazed the weathered
surfaces which produced the rainbow colours. One of our rockhound
group looked at the rainbow surface under a loop of about 20x and
said
it looked “bubbled”. It does. The corners are rounded which fits in
with the notion of melting and glazing.

Under a loop of about 20x, the colour is quite stunning. I
thoroughly enjoy observing these surfaces in good sunlight and under
the loop but as I said above, I have no idea how jewellers might work
the stones, if at all. The dark, rusty-brown background detracts from
the rainbow effects and the “splotches” are small. But who knows what
lies deeper inside the deposit as there is an abundance of this
material near the surface.

Iridescence seems to have to do with thin films or layers as we read
at http://www.webref.org/geology/i/iridescence.htm and in this case
they seem to only coat the weathered surfaces along natural fault
lines. As we read at http://en.wikipedia.org/wiki/Iridescence the
word comes from Gk “iris” = rainbow. And the complete rainbow is
found on these rock faces.

I have a nice sample here which shows all the colours of the rainbow
across a surface of about 15 mm x 5 mm. The entire piece of host rock
is about 100 grams and we would be happy to mail it to someone who is
experienced in working with labradorite, on a no cost/no obligation
basis. You can look at it and throw it out or send it on to someone
else if you need a second opinion etc. Let me know off-list.

PtP


#10

Hi all,

I am not sure yet if the outcroppings are closer to original
sedimentary or igneous deposits. The geological maps say the
overall formation is Jurassic (the end of the dinosaur age) 

The “end of the dinosaur age” was at the end of the Cretaceous
period, which lasted from 136 - 65 mya. That’s when nasties like T.
rex were still hunting /scavenging.

Scott
Nature’s Way Jewelry by Scott