I've been busy with fall cleanup and my daughter's birthday (she's
turned 10 a few days ago), that I haven't kept up on my hobby.
Then something really wierd and wonderful happened.
A neighbor, knowing I did silversmithing, gave me an entire BOXFUL of
raw Idaho star garnets. A good 10 of them were decent crystals about
2 centimeters diameter or better.
20 or more were crystals at least 1 centimeter in diameter. The rest
are not significant enough to discuss here.
They came from her mother, who collected them, but she herself had no
use for them. She asked me if I could use these as practice material
for polishing, on condition she could have the best five specimens.
no time limit.
Given that polished Idaho garnet goes for $100 per carat, I've just
been gifted with a potential fortune!
I have a flat lap with both steel and 3M laps.
Where to start? I think I'm in over my head! Help!!!
Andrew Jonathan Fine
Hello from Idaho where the star garnets grow. I don't polish many
garnets myself, but I come from a club that does so I will give you a
By mentioning them as crystals I assume that they have their
original crystal shape and are not just water washed pieces. The star
in the garnet is formed by needles of rutile growing in the crystal
structure. Usually the outside of the crystal has less rutile and the
area towards the center is where the stars will be. The crystals are
usually cut using one face of the crystal as the base of your stone.
The apex will be at the center. Thus, it takes a good sized stone in
order to align the stars right. One crystal would be cut into wedges
with the points all in the center.
Water worn pieces are usually examined with a drop of certain kinds
of oil on them and a concentrated beam of light which allows the rays
of the star to show up so you can orient them.
I am sure you will get some more from experienced
A few comments on star garnets and their cutting. There are some good
books out there that describe orienting star stones and before
starting to cut star garnets, I'd read through at least one of them.
A star garnet with an off center star has to be recut. Value will be
determined by inclusions and flaws, color, translucency, and
sharpness of the star. Six rayed stars are rare, four rayed stars
It is possible to cut a cab on a hard, flat lap, but it is a chore,
as the stone has to be kept moving about constantly and the curve is
made by the movement and the equipment does not help at all. Resin
backed vertical wheels or rubber drums allow you to get a curve just
by pressing on them, to some extent (drums work better than the resin
backed wheels, which have a limited amount of give). One would go
from about a 220 grit for rough shaping to a 600 grit and them
possibly a 300 grit for pre-polish before polishing. Polish with 14K
diamond or finer or with alumina (Linde A) or with a chrome oxide
If I were to cut garnets on a flat lap, I would use a rubber backed
disk attachment and a flexible pad charged with diamond. These are
put on the disk with a stick and peel adhesive and there are
charge-able pads and those bought already impregnated with diamond.
Just get the diamond grits you need. Of course you will need to dop
up the stone on a wooden dowel or a rod or nail with wax or glue.
While you might come out with some good stones, be aware that by the
time the stone is cut and oriented, it may be quite a lot smaller
than the rough. Also, what you have may or may not show a clear star,
be of good color. or be clean enough to be worth something. If this
all seems rather complicated, you might want to have the stones cut
on shares by a lapidary.
Possibly you could trade metalwork for stone cutting. Good luck!
In addition to the problem of orienting for the star, it can be
frustrating when it is time to polish. I have found that the best
final polish (after a decent pre-polish) is tin oxide on canvas or
leather. Polish comes up like wiping wax with a hot knife. Felt might
work, too, but I haven't tried that approach.
Good luck, and have fun!
I swear the stones were larger before I measured them with calipers
I sorted the stones into three basic levels of quality: basic,
advanced, and final.
Finally, there's cabochon quality.
Basic stones are those I would probably not shed tears over losing:
The crystal structure is either mostly or entirely intact but there
is heavy mineralization on two sides. These are the stones I want to
play with to find out the proportional distance toward the stone's
center where the stars begin to show.
Advanced stones are either entirely intact bit with one side
mineralized, or is otherwise perfect except for one or more pitted
sides or broken points. These are where I would learn how to make the
most of a stone.
Final stones are precisely that. the stones of such high quality
that I would
want to have plenty of experience before even making an attempt.
Cabochon quality stones have an entire half either broken away or
Here's my stats:
Grade/ Average Diameter/ Quantity
BASIC 8mm 78
BASIC 10mm 47
BASIC 12mm 30
BASIC 16mm 18
ADVANCED 5mm 84
ADVANCED 6mm 22
ADVANCED 7mm 39
ADVANCED 8mm 37
CABOCHON 8mm 62
FINAL 3mm 40
FINAL 10mm 20
FINAL 12mm 14
FINAL 14mm 77
These above were all the stones I did not throw aside into a jar as
useless: mineralized all over, mineralized seam splitting stone,
twinned crystals, or fragments.
The total count is 568 stones, about 60% of the original package.
I need help understanding what my plan of attack should be.
I can't just dive in, not with a package this large. I need to be
thinking like general Sun Tzu here, and I need help from you, the
general staff, what the plan should be.
Which size stones are too small to be worth my time? After I finish
what grit of sanding or micron of polish should I expect to see the
beginnings of asterism? What grit and polish sequences is suggested
for these stones? Are stones considered more valuable as whole
spheres or as cabochons? Is there some way I can get asterisms from
some of the irregular pieces for inlay purposes?
(I have available a standard set of diamond wheels, a set of
foam-backed 3m abrasive wheels, a cerium oxide polish wheel, and at
least some foam wheels upon which I can place diamond paste. The 3m
and the diamond pastes are in microns, please keep that in mind).
When I attach the stone to the dop stick with wax, should I have
either a point or a facet at the apex to create asterisms? How far
into the stone, in percent, must I sand away to see asterisms? Will I
only be able to see it with my Optivisor?
Thanks in advance for answers to all the above questions.
Andrew Jonathan Fine
Hello Andrew; It is evident that you have gone to a lot of work to
grade your garnets.
I hate to tell you this, but if my memory serves me right, the last
time someone asked for star garnet on this site there
were few answers. Consider that many of the artists here work
primarily with metals and buy their stones. The ones who shape their
own are in the minority and they may not be online or have the time
to reply in such detail. Have you checked the archives to see if
there is on the subject? I looked around the website and
the isn't that detailed, is it? The site that comes up
from Stewarts Rock Shop on star garnet will give you some help with
Well, here is a little more input for you.
There have been good articles in the past about this in Rock and Gem
A soft cover booklet on Star Stones was published sometime ago and
would be helpful. Look for it on E bay or perhaps on Amazon for out
of print books You mention garnets with mineralization to them. I am
not sure what you mean. If the side of the stone is coated with a
blob of rock material such as the metamorphic shist matrix the stones
grew in it may be that the crystal is perfectly good underneath it
and you would just grind it away. In other stones the garnet grew and
included the surrounding matrix and may have the right shape but be
completely incorporated with the mica and junk. Some stones called
sand garnets are already just crumbly grains and not useable. Other
garnets have been weathered on one side by exposure to the elements
until they are not solid on that side.
Not all the stones found at the garnet collecting site are
necessarily star stones. I can't give you the exact percentage, but
my guess is that it is about ten percent.
The rutile that forms the reflective star rays gives the stone a
darker appearance. Sometimes putting damp stones on a clear pyrex pie
pan and shining a light through them from underneath will help. The
clear grape juice colored stones don't have inclusions.
One clue collectors look for is a "raisin" appearance to the outside
of the stone especially in water worn pieces, because the rutile will
wear away faster.
Having a flaw or two does not necessarily mean a star garnet is
Some feel that water worn garnets can be inspected better if they
are tumbled first. By my geologist friend said that being a
metamorphic rock, they often have a lot of pressures inside that can
make more cracks during the tumbling.
The outside flat crystal face would be down on your dop stick to
form the bottom of your stone and the point from toward the center of
the crystal would be on top so you could cab a high dome.
I really appreciate your advice. I have indeed looked all over the
internet on advice to polish these properly and have come up with
Three years ago I visited Clarkia and had found a few stones of my
own. Stewarts Rock Shop probably doesn't remember that I called them,
but when I asked, the person I talked with refused to give out any
saying they didn't want to reveal their secrets to the
In other words, they felt to me about as welcoming as an Idaho
blizzard regarding this.
I am grateful for your advice that more of the stones I had graded
away are far more recoverable than I thought. I'll revisit them,
thanks to you.
I'll try looking up for that book "Star Stones". I think it might
make a lot of sense to have proper intel first before I make my
Do polished Idaho garnets that have no star, have any value at all,
just for their relative rarity? Or are they more or less treated
like agate and jasper as far as usage in jewelry is concerned?
Andrew Jonathan Fine
Andrew, I polish garnet on my lap with cerium oxide on felt. Your
laps with the diamond polish should also work. There is no fixed
depth to see the asterism, you try to orient the stone on the dop so
you are looking vertically down the optical axis, then cab away. When
you intersect the rutile crystals in the rough, the star should show
up. Have fun cutting.
BTW, there is no secret to cutting, sometimes the asterism is more a
matter of luck.
All right, Andrew, I can see you are working hard at this. I can't
locate my star stones book right now. However, I am sitting here with
a whole library of folders on different semi precious gems and their
cutting properties for cabochons and such. not faceting. And there is
one folder on garnets. I think what will do you the most good right
now is a paper that one of our members prepared and gave out at a
lecture at the Hell's Canyon club. He copied pages from several
different books without giving the sources but I promise you it will
give you what you need.
My husband and I are old codgers who have just moved in with our
daughter and son in law with one side of the house our "apartment".
Our copy machine is not working now and access to the disc for
reinstallation to our computers is inacessable at the moment. But if
you will e mail me your address off list I will go to the library and
copy the paper for you and mail it to you. All that I ask is that you
pay the copying price and the postage after I send it to you. It may
take me a couple of weeks.
Most of the garnets from up at Emerald creek are too dark to really
show much color other than almost black when made into a cabochon.
You could try it on some of the stones that will look like clear
grape juice when you shine the light through them in the pyrex pie
pan However, it will take a good polish. On the other hand, the sands
are used as abrasives on sand paper.
There are places where faceting grade lighter red orange material
has come from in the past. I once saw a propieter at a store in
Moscow, Idaho, measure out in carets a packet for a man from
Pennsylvania. Our club does not go to Emerald Creek anymore. The
yield is less than exciting. The Forest Service is keeping off limits
all the other sites around there and woe betide the person who tries
to prospect there. He may end up in court with a healthy fine.
One illustration of a star garnet on the internet has a flaw running
through it and what look like little polka dots in it. They may be
flaws, but some of the rutile crystals can be rather hollow and take
up the polishing compound in their openings, and make dots. Perhaps
rubbing the stone dry with dry fels naptha soap before the polishing
and scrubbing it well and repeating the soaping for each of the finer
grits and polish would help those from showing up as dots.
Now, European lapidarists in days gone by would actually hollow out
the back of the garnets to allow more light through. and also put a
reflective backing behind it. Something to experiment with if you
have lots of time to play around at it.
There are also some grossular garnets in another central Idaho area.
But they are brownish tan and not gem quality.
I haven't really gotten aquainted with Stewart's Rock shop yet. I
guess they do cut garnets. But, imagine what your reaction would be
if for the last 35 years or so everybody in Southern Idaho that went
up to Emerald Creek or inherited a bunch came into your shop and
asked for free instructions. It really takes some personal lessons or
reading up on the subject to be able to do it right, as you will
understand after I send you the instructions.
Hope this helps a bit.
Rose Alene McArthur
Original Message --
Andrew, you asked:
Do polished Idaho garnets that have no star, have any value at
all, just for their relative rarity? Or are they more or less
treated like agate and jasper as far as usage in jewelry is
I have seen tumbled Idaho garnets that were flawless, and could be
used in wire wrap or cemented jewelry. I was lucky once to find among
my few tumbled pieces one that was transparent enough to be faceted.
It was on the dark side, though.
Just use them for their color and attractive polish without worrying
about rarity (or not).
I can't seem to find an off-site email link for you.
Can you find mine and email me?
Andrew Jonathan Fine