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Getting good polish on spinel


#1

Hello Everybody,

I am new to this forum. We are manufacturers of colored gemstones
and studded gold jewellery. We are manufacturing calibrated Emeralds
and Tanzanite.

Recently I purchased Spinel rough. In polishing i am facing
difficulty to get good polish. I am using diamond powder on tin
plate.

Please tell me how can i get very good polish on Spinel.

Thank you

Regards,
Jignesh Shah


#2

i use cerium oxide on felt.

john


#3
Recently I purchased Spinel rough. In polishing i am facing
difficulty to get good polish. I am using diamond powder on tin
plate. 

I usually use 60K diamond on a Darkside or BATT lap, but I have used
AlOx as well. What grit diamond are you using? What lubricant?

Al Balmer


#4

Jignesh-

You don’s say what mesh diamond you have tried. You would need
50,000 or finer for a good polish. I have doubts about the efficacy
of “tin plate” although it might work if the tin layer is thick
enough.

I have had no problem getting a good polish on spinel using aluminum
oxide on a solid tin lap, also with 100,000 mesh diamond on BATT or
Darkside laps, using light pressure to avoid facet rounding. The
latter laps are available from many dealers in lapidary equipment, or
from Jonathan Rolfe, the manufacturer. Many other combinations will
work, too, but I have not tried them myself.

I hope this helps.
Richard D.


#5

I’ve polished synthetic spinel on a tin lap with 50,000 grit
diamond, it works. Are you using oil lubricant? Diamond is
hydrophobic, water will cause the diamond particles to stick together
in clumps, you need oil based lubricant. Any oil is usable, not
water.

If you don’t want to get your lap oily, aluminum oxide plus water
would work too.


#6

Thanks for your valuable I’m using 50,000 mesh powder
on tin plate. I will try 100000 mesh powder. Hope to get very good
polish.

Thanks once again.

Regards
Jignesh shah


#7
Recently I purchased Spinel rough. In polishing I am facing
difficulty to get good polish. I am using diamond powder on tin
plate. Please tell me how can i get very good polish on Spinel. 

You should joint the USFG discussion list. Several thousand gem
stone faceters on the list will give you many suggestions for
resolving your problem with polishing this and any other gemstone
material

Best regards,
Robert P. Lowe Jr.


#8

Back in the 80’s I worked for Capital Technologies International as a
facetor and polisher of We used Lux machines that faceted
and polished 14 stones at a time. When polishing we used a copper lap
with oil and 50,000 grit diamond for polishing. I no longer do this
kind of work but I’m sure the technology has changed some.

Chris Hierholzer


#9
I'm using 50,000 mesh powder on tin plate. I will try 100000 mesh
powder. 

If you don’t have success with 50K, I doubt that 100K will help.
Your problem is elsewhere, probably the lap. I have never heard of a
tin plate lap. Usually, diamond powder embeds in the surface of a
polishing lap to around half the particle size. I don’t know how
thick the tin plating is, or what the substrate is. I also don’t know
whether the lap has been contaminated by a foreign substance or
larger diamond grits. The recommendation of Gearloose products was a
good one. I would recommend starting with the Darkside, since it’s
more forgiving than metal laps and can be used for both diamond and
oxide polishes.

Al Balmer


#10

This is a peripheral issue to the initial question in this thread,
but I thought it might add to the discussion. I have mentioned Henry
Hunt’s books previously, and I was re-reading “Lapidary Carving for
Creative Jewelry” because I am about to mix up a batch of paste for
adding the various grits of diamond to, and I wanted to be sure I
remembered his instructions correctly. In the back of this book he
devotes some pages on how to carve and polish particular stones. He
discusses (and gives step by step instructions) the spinel in
reference to carving rather than faceting. This is also part of his
campaign to get carvers to use synthetic stone as a continued carving
material, so these couple of pages devoted to polishing the spinel
may have no value to natural stone, or faceting. It has been my
experience that many techniques used for one, may be used for the
other. I must admit I have no authority in discussing faceting, as
all I have ever accomplished in that area is a few free form faceted
projects done for my own satisfaction. Another book “American
Lapidary/Designing the Carved Gemstone” by Henry Hunt, along with
this first one has many examples of faceted stone that has also
incorporated carving with the faceting (way out of my league) done by
Micheal Dyber and many others who are accomplished in both fields.
This leads my to belief that the info in the first book would have
some pertinence in accomplishing your goal. Both books are readily
available even in my small local rural libraries, so I would assume
that the info would not be hard to track down if you choose. Just in
case… Thomas III


#11

Different stones do sometimes require different methods to get a
good polish, anything from different compounds to differing speeds,
reversing lap direction, etc. You might want to ask this question on
the US Faceter’s Guild list.

Lorraine