I’ve heard of making burnishers out of agate. Since I’ve got a lot of
agate sitting around I thought I would make a couple when I run out
of other things to do…
What are the advantages of using an agate burnisher?
Rick Copeland
rockymountainwonders.com
An agate burnisher has a smooth, hard surface that doesn’t rust. When
making an agate burnisher try to use a piece that’s solid without
banding, inclusions and fortification. These make beautiful
burnishers but they’re prone to crack.
RC
What are the advantages of using an agate burnisher?
To be precise it is chalcedony that we want. Agate is almost the
same, but due to chalcedony is cryptocrystalline mineral, the finish
is especially good.
Leonid Surpin
To be precise it is chalcedony that we want. Agate is almost the same, but due to chalcedony is cryptocrystalline mineral, the finish is especially good.
Agate is also cryptocrystalline. In fact, agate is a variety of
chalcedony.
From Agate Factsheet and Mineral Information Page
The cryptocrystalline varieties of quartz may be separated into
two types; fibrous and microgranular. Chalcedony is the general
term applied to the fibrous cryptocrystalline varieties. Agate
is an example of a fibrous cryptocrystalline banded chalcedony
variety of quartz. Carnelian, Chrysoprase and bloodstone are
other chalcedony varieties. Chert is the general term applied to
the granular cryptocrystalline varieties of quartz, of which
flint and Jasper are examples.
Al Balmer
Sun City, AZ
I’ve made a few… just like making a cab. Given most “agates” are
banded… I use solid color jaspers. Has anyone ever tried making a
burnisher from jade? It is slightly less hard when compared to agate,
but would be much less prone to breakage. Agate burnishers also do
not retain heat as readily as steel burnishers… making them a
better choice for Keum Boo.
Agate is no less cryptocrystalline than chalcedony. Indeed, agate
is chalcedony.
Hans Durstling
Moncton Canada
I make burnishers from nephrite.
What people commonly call 'jade is one of two: jadeite or nephrite.
Nephrite is definitely tougher and is fibrous; jadeite has a sugary
texture.
kpk
Agate is no less cryptocrystalline than chalcedony. Indeed, agate *is* chalcedony.
One has to distinguish between Chalcedony as species and Chalcedony
as variety. The statement that Agate is no less cryptocrystalline
than Chalcedony is patently wrong. Agates frequently include layers
of Opal, Amethystine, and etc.
Leonid Surpin
Agate is also cryptocrystalline. In fact, agate is a variety of chalcedony.
One has to be careful using gemological definitions.
Chalcedony is gemological species, which includes Agate as one of the
varieties, so the above statement is true. However, in my post, I
directly compared Agate and Chalcedony, which should have been a clue
that I am referring to Chalcedony as cryptocrystalline variety of
Chalcedony as a species, which includes cryptocrystalline as well as
microcrystalline varieties.
Internet is a great source of but it could also become
a great source of confusion.
Leonid Surpin
I make burnishers from nephrite.
Kevin knows…
I’ve made a few myself - I have one in my bench right now…
It makes little if any difference what stone it’s made out of, as
long as it has certain characteristics: Hardness of 7 or better (I’d
thought of making them out of ruby laser rods…), clean texture, able
to take a fine polish. Agate, as opposed to chalcedony, works just
fine as long as it is clean. That is, if the bands are solid and not
cleavages. That’s easy enough to see.
A Google of “agate burnishers” with quotes brings up much.
Gildedplanet. com has a whole online catalog of shapes and sizes…
Agates frequently include layers of Opal, Amethystine, and etc.
… in which case they are not agates at all - but a mixture of
agate etc.
Also…
Although you used to be able to tell a nephrite/jadeite stone from
the slightly “orange peel” surface the use of diamond abrasives in
polishing now means that the stones often have a perfectly smooth
surface.
Tony Konrath F.G.A
Agates frequently include layers of Opal,
That’s a new one; could you give more info on “agates with layers of
opal”?
kpk
Agates frequently include layers of Opal, Amethystine, and etc.
Then the rock isn’t all agate, is it?
Al Balmer
Sun City, AZ
Although you used to be able to tell a nephrite/jadeite stone from the slightly "orange peel" surface
If that was/is the case (orange peel) it’s because of poor lapidary
technique.
One can still have ‘orange peel’ even with diamond compounds.
‘Orange peel’ is not uncommon with materials that tend to undercut.
kpk
That's a new one; could you give more info on "agates with layers of opal"?
Opal is frequently substituting for Chalcedony during formation
processes.
Opal formulae is SiO2 * n(H2O), n - is a variable indication how
much water is present.
Chalcedony is cryptocrystalline form of Quartz, and formulae is
SiO2. As you can see, chemically they are twins. Some even speculate
that variety like Milky Chalcedony is simply a very old, dehydrated
Opal.
Leonid Surpin
... in which case they are not agates at all - but a mixture of > agate etc.
Agate is a variety of Chalcedony (species), when perfectly formed,
does contain layers of Chalcedony and nothing else. However, once
again, Chalcedony as species and not a variety. That includes
chrysoprase, carnelian, onyx, bloodstone, and several others. Some
gemological references like GIA, even include Jasper. More often than
not, Agate contains layers of other minerals, which do not belong to
Chalcedony, so the assertion that presence of other minerals
disqualifies Agate from been Agate, is not supported by anything I
have ever read on the subject.
I am always welcome the opportunity to learn something new, so if
there are some gemological reference, which supports your position,
I would be very much inclined to be acquainted with it.
Leonid Surpin
I am always welcome the opportunity to learn something new, so if there are some gemological reference, which supports your position, I would be very much inclined to be acquainted with it.
I supplied one which didn’t get published. But, let’s do it the
other way around. Why don’t you supply references which support your
position? I’m sure many of us would be interested.
Al Balmer
Sun City, AZ
Some even speculate that variety like Milky Chalcedony is simply a very old, dehydrated Opal.
That would require more than just dehydration, since opal is
non-crystaline and amorphous, a solidified silica gel, more like
glass, formed into little spheres which have semi merged together,
leaving variable spaces between which gets filled with the water
content in opal. The more the spheres have merged, the smaller those
spaces, and the less water. Fully dehydrating the opal might fully
merge those spheres, leaving a fully solid mass of the amorphous
silica gel, but it wouldn’t automatically mean the gel had
crystalized, which would have to additionally have happened in order
for the material to be a chalcedony. Perhaps time would do that
under the right conditions. Old enough glass starts to crystalize
(part of the source of the wonderful irridescent patina on ancient
glass) But opal’s silica gel is not precisely the same as a glass, so
I don’t know if time alone would do this to the opal. Do you?
Peter
Old enough glass starts to crystalize (part of the source of the wonderful irridescent patina on ancient glass) But opal's silica gel is not precisely the same as a glass, so I don't know if time alone would do this to the opal. Do you?
In gemology there is a saying that “I believe in the theory until it
changes, and then I believe in another one” Opals are weird. You
stated the generally accepted theory and most gemologist agree with
it, but than there are things like opals forming inside bamboo. That
throws a monkey wrench into it. There is book “Jewels” by V. Finlay.
She describes a guy in Australia growing opals in jars. He claims to
discover some process. I have my doubts about the story. Miners can
be very creative in their humor, but if it’s true, than the whole
theory goes out of the window. My personal feelings is that nobody
wants to spent enough money to do real research, so we kind of
coasting along with one theory, until another one will be accepted.
Leonid Surpin
I supplied one which didn't get published. But, let's do it the other way around. Why don't you supply references which support your position? I'm sure many of us would be interested.
Chalcedony, in gemological circles, treated with disdain because it
is not expensive, so gemology books do not spent much time on it. But
mineralogical references are quite detailed. I am most familiar with
Fersman, due to my educational background, but I am sure that Dana
will be just as good.
This should be done as a blog, but time is of the essence, so in a
few words as possible. Chalcedony forms crusts, amygdules (gas
cavities), and nodules, act as vein filler, cements Breccias
(sedimentary rocks), and can even form as a pseudomorphs. A lot of
gems like Turquoise, benefit from presence of Chalcedony. Due to all
these different modes of formation, Chalcedony is classified as
fibrous (which in turn sub-divided into parallel, spherulitic, and
feathered), fine-grained, and ultra-micrograined. All this abundance,
in combination with metallic salts present during formation, give
raise to many gemological varieties. For example - if Nickel is
present, the chalcedony is called Chrysophrase.
Agate is defined as variety of Chalcedony, characterized by a
pronounced macroscopic banding. Agates are mineral aggregate, whose
composition includes other minerals, as well as Chalcedony.
Dollinger lists more than 30 minerals, which are included in agates.
This is a vast subject, so it is better for those who are interested
to pick a book or two about agates, then me, trying to cramp
into a few lines.
Since, discussion started from what is the best material for making
a burnisher - simply to say agate is not precise enough to have any
meaning. Burnishing, in it’s own right, can be a subject of many
volumes. From goldsmith point of view, I want to use something which
gives me the best chance of success. Some agates are very good for
this, and some are not. Limiting definition to Chalcedony (variety)
is more precise.
Leonid Surpin