Back to Ganoksin | FAQ | Contact

Faceting, solutions to match RI


#1

As I may have mentioned, I’m starting to try to learn to facet. It
is going slowly, as I don’t have much time to put into it, but I
enjoy it.

I have read about the use of solutions that match the RI of stone to
reveal the internal condition of the rough. What I want to know is,
are there things I can use that I would have around, or do I need to
buy special substances for this purpose? I’ve seen how wonderfully
this can work when I dropped a moonstone into opticon and it
disappeared except for the fracture, and an unearthly glow. But
opticon is not practical for testing rough!

I have a jar full of pale aquamarine that is so beat up on the
outside that I can’t tell whether any of it is usable. What do I pop
it into to make it “disappear”?

Thanks for any and all help!
–Noel


#2

http://tinyurl.com/5d7b9

that is a list that I found for refractive indexes in a very fast
search… just look at the liquids, and find one that is closest
to the RI of the stone you want to use it with. I know I have seen
a list of more liquids that can be easily used for but I
cant remember many of them.


#3

Firstly, as I have noted on this forum several times in the past and
am willing to do so again especially since this is a query from
Noel: for those interested in stone and/or lapidary an essential
book is “Gem Cutting” by John Sinkankas. It’s basic reading.

Gem Cutting: A Lapidary’s Manual
By John Sinkankas

http://www.ganoksin.com/jewelry-books/us/product/041207821X.htm
Price: $67.95
Media: Hardcover
Manufacturer : Chapman & Hall
Release data : 01 October, 1984

Now for Noel specifically, as you mention there are solutions with
RI’s that match or are close to RI’s of specific materials; i.e.,
opal and glycerin. Sometimes the answer is to polish a window into
the rough.

One caveat, don’t divide material into faceting grade and caboshon
grade. Remember inclusions are not flaws; they are nature’s
fingerprints. The R.I. of aquamarine, one of the beryls is 1.56-1.6
according to John Sinkankas. I don’t have time to research the name
of a solution that would be appropriate; I have to get back to my
rocks.


#4

Hi Noel,

There is a liquid called Italdo Refractol. My label has Bob-A-Lou
Rock in Saginaw MI as manufacturer(?). Perhaps Kingley North or
Graves might have it. It has a refractive index 1.567 and the label
advises that it is odorless and nontoxic. I bought mine in a
lapidary store that sold faceting rough. The Gemmologists"
Compendium by Robert Webster has a comprehensive list of different
chemicals and their refractive indexes on pages 134-135. No info on
how nasty they may be to work with but when you see bromo as part of
a name it is not usually a good sign!

Gemmologists’ Compendium
By Robert Webster, E. Alan Jobbins

http://www.ganoksin.com/jewelry-books/us/product/0442238851.htm
Price: $14.95

Media: Hardcover
Manufacturer : Van Nostrand Reinhold
Release data : 01 January, 1981

HTH,
Karen


#5

Noel, there are plenty of things you may have around to use. Here’s
a list that may help a bit:

Liquid			RI
Water			1.33
Alcohol			1.36
Turpentine		1.47
Olive oil		1.47
Pure glycerin	1.47
Clove oil		1.54
Cinnamon oil	1.59
    I have a jar full of pale aquamarine that is so beat up on the
outside that I can't tell whether any of it is usable. What do I
pop it into to make it "disappear"? 

The cinnamon oil should work best for aquamarine, which is 1.577 to
1.583, but the clove oil is a close second. The best option, if you
want serious diversity is to get ahold of some methylene iodide and
benzyl benzoate. Gemologists mix these fluids mostly for estimating
specific gravity, but the liquids’ RI changes at the same time. You
can get up to 1.74 with straight MI. One more liquid is acetylene
tetrabromide, with an RI of 1.64.

If you’d care for instructions on mixing methylene iodide and benzyl
benzoate for RI, email me off-list and I’ll be happy to try and
explain. You’ll eventually need certain, small sample gemstones
(rough is fine) to set the SG of the liquids. Either that, or a
refractometer to set the RI, but refractometers are probably more
expensive than your purpose would justify.

James in SoFl


#6
   I have a jar full of pale aquamarine that is so beat up on the
outside that I can't tell whether any of it is usable. What do I
pop it into to make it "disappear"? 

Noel,

The usual liquid used for immersing beryl for gemmological purposes
is Benzyl Benzoate (RI approx 1.56). It is colourless, oily and quite
smelly, but does just the job with stones such as quartz and beryl.
Be careful when using it, like all chemicals! It is not a good idea
to mix Benzyl Benzoate with plastic (i.e. use a plastic container) as
it attacks plastics! At least in my experience it did when used this
way.


#7

Hi Noel,

  I have read about the use of solutions that match the RI of
stone to reveal the internal condition of the rough. What I want to
know is, are there things I can use that I would have around, or do
I need to buy special substances for this purpose? 

There is a substance used by cutters called: “Refractol”. It is
odorless, non-toxic and has a Refractive Index of 1.567 - which is
very close to Beryl - such as the Aqua you are working with. Using
Refractol, you should be able to clearly view into most gem rough
that has a low-to-mid RI range. In addition, you may find it helpful
to use a low-intensity light, back lit of the rough you are viewing.

When I need to use Refractol, I generally wear the same pair of
latex style gloves. This helps to keep my hands clean and to not
transfer substances from one item to another. Then, you will need to
clean the rough thoroughly with denatured alcohol or your favorite
de-greaser/cleanser prior to dopping.

Roger Dery
@Roger_Dery
Spectral Gems, Inc.
Rare Gemstones - Exceptional Faceting - Genuine Colored Stones


#8

GEMSTONE & MINERAL DATA BOOK by John Sinkankas has all the
you would wish on this , and other gemological subjects.
The one drawback to this book ( 350 pages ), is that there is SO
much and the organization could have been better. I
highly recommend it Available in trade soft back and hard back. It
is out of print and still in demand.

I had 2 soft back copies, gave 1 copy to my school and bought a
hardback copy. I have 1 soft back copy to sell. The books are the
same except the paper and binding quality. I have several other
duplicate copies of other gemology, or appraisal books ( in good
shape ) which are surplus . I would like to sell these so as to buy
other books.

TIP - The newest copy of HANDBOOK OF GEM IDENTIFICATION BY Richard
T. Liddicoat comes in soft back only. After a month the pages fall
out of the glued in binding. So Get a printer to cut down the pages
and punch holes to fit a 6 X 8 , 3 ring binder. I got a 3 in wide
back Avery binder. The pages fit very well, and I can insert
additional pages with comments and up dates into it. This saves
time, and supports the identifications.

Time became important at TIJT Paris Tx.'s Gemology School. We were
required to properly identify some 450 gemstone specimens in the lab
portion, for graduation. This was the hardest part of the 40 hr /wk.
1 semester class.

The British F.G.A has opened up a Gemology School now at TIJT. They
wanted to open a school in the USA and the existing school ( G.G.S.)
shared many similarities with FGA.

Robb.


#9

Karen,

Graves does carry Refractol…it is item 05-320 on page 72 of the
Graves catalog. You can find it by going to the on-line catalog at
www.gravescompany.com and clicking on ‘jeweler’s supplies’ and then
’gemological’.

You can call, use snail mail or use the handy secure on-order form.

Cheers from Don in SOFL…I work at Graves.