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Agate or Jasper?


#1

Hi Yall; to my knowledge jaspers are opaque to no light at all… It
depends on the majority of the matrix. Many are jaspagate as they
often form together in layers. I have always considered agate to be
translucent to transparent as anything else is either dreck or
’jaspagate’. On the serious side, transparency makes the agate
unless it is a multicolored layered colors, no? Ringman


#2

Dave, In very simple terms:

Massive quartz with no crystaline structure, translucent, usually
with some color - such as chrysoprase = chalcedony,

Massive quartz WITH BANDING of any color usually translucent to
semi-translucent - such as Fairburn geodes, or layered-such as
amethyst lace = agate.

Massive quartz with NO banding, (i.e. amorphous) with any or many
color(s), semi-translucent to opaque = jasper,

Massive quartz with areas of color and clear areas with isolated
banding, translucent, semi-translucent and/or opaque areas = what
some term jasper-agated or jagate.

Hope it helps…this field is very confusion. Ann and Si Frasier
have been writing on this subject for many years with the Lapidary
Journal as has Bob Jones with the Rock & Gem magazine. After 30 or so
years, they still have not finished! So don’t feel bad.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry. @coralnut1


#3

Hi Dave I went to my “Gem Cutting” by John Sinkankas which I’ve
previously mentioned as an indispensible lapidary reference on this
forum. In chapter 19 under quartz one finds crystalline varieties,
then cryptocrystalline ( meaning a crystalline structure too fine to
be seen without your electron microscope) and under that heading,
agate- "chalcedony in various layers, bands, colors, patterns,
mosses, tubes, etc. Following that “Jasper- very impure chalcedony,
usually containing considerable earthy or clayey material. Generally
distinguished from agate as any variety which is opaque.” You’ll
generally find info without the “gobbely-gook”. Cryptocrystalline
and microcrystalline are not the same. These things are always
helpful when speaking with customers. In my experience there is way
too much inaccurate passed on as fact: my particular
point of annoyance is jewelers identifying a certain opal as “black
opal” which is not black opal but usually a fine colorful crystal
opal. No reflection on you Dave, I just couldn’ help myself.


#4

Dave Yes, in my opinion, it is just that simple…Partially
transparent, cryptocrystalline silicone dioxide quartz chalcedony,
is agate and can show multiple fine banding.

Other forms of the agate family / cryptocrystalline chalcedony
quartz family, are chrysocolla and chrysoprase… When these 2
materials are residing in lots of translucent cryptocrystalline
quartz, they are sometimes called “gem silica.” But really they are
simply A or AA or AAA grades of those blue and green materials…

So basically, jasper is a form of impure cryptocrystalline quartz,
usually not transparent…

If it is somewhat transparent, the material can be considered
partially agate and partially jasper

Both jasper and agate are the durable cryptocrystalline quartz…
Unlike the more fragile form of crystalline quartz, such as
crystalline rose quartz…

Agate is translucent / transparent, while jasper is more fibrous and
contains more impurities, such as iron oxides.

Hope this helps
RocknLight


#5

Hi Dave,

This may be over simplification, but observation seems to lead to
the conclusion that jaspers are opaque and agates have some
translucency or transparency to them. Could it be that simple??? 

Pretty much! And, when the opaque and translucent are intermingled,
as often happens, the material is frequently referred to as
jasp-agate. Regardless, they’re both examples of micro-crystalline
quartz.

Beth


#6

Dave -

 This may be over simplification, but observation seems to lead to
the conclusion that jaspers are opaque and agates have some
translucency or transparency to them. Could it be that simple??? 
This is a very clear summary, and close to correct. The missing

“piece” is a mention of chalcedony, which is the actual mineral
involved. The series begins with pure chalcedony which is virtually
colorless, almost transparent, and harder than 7 on the Mohs scale
of hardness due to its pure fibrous micro-crystalline structure. As
impurities are added chalcedony gains color and pattern, and moves
from almost transparent translucency toward total opacity, losing
hardness as it goes. Some authorities say the series ends with
chert/flint because most flints are considerably softer and far from
"pure". Your statement says it all, and very clearly, from a jewelry
perspective. (and YES, the vast majority of stuff sold as agate is
in fact jaspery, if not actually jasper)

Jim Small
Small Wonders


#7

Hi Dave and Group…

Funny thing…I was just digging around about this very subject…

Schuman says the jasper is usually considered a chalcedony
species…but that some sources give it its own
group…because of the fine-grained structure…

The GIA Essential Colored Stone Reference shows a fine picture of
what almost everyone calls landscape jasper as landscape agate…

It might just be me, but I think the gemology/geology
group-species-variety classificiation is in some cases murky at
best…

Many years ago when studying biology, I got the binomial
nomenclature thing down by a nonsense sentence…“King Phillip Came
Over For Good Sex Variety” or…
Kingdom-Phylum-Class-Family-Group-Species-Variety…It’s how one
figures out where a living thing is classified…

So this intent of the group-species-variety in gemology is
understandable…

Dang if I can figure out how the labels are applied consistently,
though…

Gary W. Bourbonais
L’Hermite Aromatique =A9


#8

hello everybody, how agates vs jaspers was explained to me once is
that agates let more light through than jaspers - in other words,
the more opaque and solid the stone, it’s a jasper. a stone with
areas of translucence (?sp) is an agate. i’m sure there’s more to
the nomenclature than this, but this is how i’ve always separated
the two. susannah


#9

All, Basically Jasper is “dirty” chalcedony. Enough said…(smile) On
a more serious note, I have a BOOK on jasper…problem is that it
is in Russian. I’m not having any problem understanding the Russian
photographs ( smile again) , but the cyrillic text is daunting me.
Is there anyone out there who can translate it for me ? The Russian
text is thirty pages long. There is a “summary” in English, but it
is just two pages. I am curious to know what the Russian text says.
The best feature of the book is that it has approximatly two hundred
color photographs. Apparently the Ural Mountains constitute perhaps
the largest Jasper deposit in the world. It is interesting to note
that many of the types that we have considered to be rare or unique
also occur there. Another interesting aspect of the Russian jasper is
that it occurs throughout the Ural Mountains. The Urals are thought
to be a “suture” zone wherein ancient continental plates collided
and produced subduction metamorphism. Our own coast ranges on the
west coast could be said to be a suture zone inasmuch as about
twenty million years ago the Pacific plate was being subducted. Thus
we have a wide variety of jaspers throughout the coast ranges. Ron
at Mills Gem, Los Osos, CA.


#10

Dave & All, I agree with all the posts so far. To me the importance
of nomenclature is to reach a mutual understanding of what the item
is that you are describing. Agate and jasper terms can be confusing,
but when I am selling a piece I describe to the buyer exactly what
the piece is and why I am describing the piece in that manner. Some
of my cabs are mixtures of agate and jasper. Some of my agate cabs
are opaque. None of my jasper cabs are translucent. I just take the
time to reach a mutual understanding. That is what disclosure is all
about.

Gerry Galarneau
@Gerry
www.galarneausgems.com


#11

Hi Dave, The best description I found in regard to agates and jaspers
was in “Fifth Edtion GEMS Their sources Descriptions and
Identification” by R. Webster

From what I read I understood the following:

It seems that Jasper is a more dense material. Banding is present
in jasper however in agates the banding is concentric.

The book also mentioned that Jasper appears in heavy sedimentary and
metamorphic conditions and with iron ores, cavity filling, or
nodule.,whereas agate is found igneous or lava situation and
possibly formed of deposits of silica in cavaties. Colors in agate
are usually light. (Onyx is also an agate)

Diane Sadel
http://www.sweetgemstones.com


#12

I would add that, while chrysoprase is chalcedony colored green by
nickel, chrysacolla technically is not a quartz mineral at all- it
is copper carbonate, and not even particularly cuttable unless
stabilized, or at least partially silicated. The "gem chrysacolla"
one hears about is actually chalcedony colored blue by the presence
of chrysacolla.

Lee Einer


#13

Into what category would ‘crazy-lace agate’ fall? It appears
opaque. Dee


#14

Sorry Lee, Chrysocolla is not a carbonate…it is a silcate of
copper. And, while it is not a quartz family gemstone, it frequently
is intermixed with chalcedony and/or opal thus making it more or
less workable for lapidary applications. Pure chryocalla is much too
soft to be used as a gemstone. Ron at Mills Gem, Los Osos, CA.


#15

Dee,

IMHO, Crazy lace “agate” is an enigma! In some cases it is more
jasper than agate but often it is banded so it can also be called an
agate, even though it is normally opaque but on occasion somewhat
translucent!? Take the Noriega version of this stone which is called
CLA but is most certainly a jasper. Of course, certain persons with
an aim toward making money are now calling the Noriega stone - the
Rosetta Stone so they don’t even put it into the CLA catagory. Crazy
isn’t it?

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut1


#16

Dee - Crazy lace agate is one of those hybrids, techniclly a
jasp-agate. It was named in El Paso, TX when it was first imported in
the 1950s, and the name stuck. If you hold thinly sliced crazy lace
up to a bright light source you can see that it has both opaque and
translucent layers; hence jasp-agate as a designation. The varietal
names of the quartz-family gems are incredible! Sy and Anne Frazier
have been doing a book for many years on the quartzes which should
include almost all of the names when it is eventually published.
They have repeatedly solicited lapidaries for their help via Lapidary
Journal on this topic.

Jim Small
Small Wonders


#17
   Into what category would 'crazy-lace agate' fall?  It appears
opaque. 

Hold a thinner piece to the light and you’ll find that at least many
of the layers, are not opaque. And more important, a close look
shows that it’s a highly layered structure, like more sedate agates,
except that with crazy lace, the layers are all roiled and jumbled
around… Still, thie stuff is built up in layers.


#18

Thanks, Ron-

I stand corrected.

You are absolutely right in that chrysacolla is CU SiO3, not a
carbonate. It is only cuttable if it is either well-silicated (a
well-silicated silicate?) or stabilized. I have cut a fair amount of
chrysacolla, and would say that chrysacolla is/ occasionally /
sufficiently intermixed with either chalcedony or opal to make it
cuttable. I would not say that this occurs frequently. Soft,
chalky, crumbly chrysacolla is common as dirt, but well silicated,
cuttable chrysacolla is not plentiful, and the top grade
chrysacolla-impregnated chalcedony is scarce as hen’s teeth- which
is why the top grade stuff sells for thousands of dollars per pound.

Lee


#19

I have slabs of Red and Gray Crazy Lace “A g a t e.”

What I consider Top Grade Crazy Lace Agate, is Transparent /
Translucent, yet the slabs still show all the wonderful crazy lace
patterns

In other words, when a slab is held up to any dim or bright light
source, the light can easily be seen through the slab, as well as,
my fingers can be seen through the opposite side of the slab.

Other slabs of Crazy Lace material I have are NOT transparent, nor
translucent. They simply show the great patterns, but have little to
NO light transference through the slabs. Technically, these types of
no light transference slabs, should be called Crazy Lace Jasper, not
"Agate."

But, old habits die hard and very few people, myself included, will
change the name appropriately, when faced with slabs showing any
light transference or not.

Bottom line, if light is not able to transfer itself through, let’s
say…oh…approximately a 1/4 inch slice / slab, of any material
in question, then it ain’t agate : )

Hope my opinion helps

RocknLight


#20

That would mean that I have some really nice Dry Head fortification
jasper cabs, and some Imperial Agate slabs sitting around. Is the
matter strictly one of translucence? Or should we give deference to
the names which have historically been assigned to these materials?
If we go too far down the road of assigning names by the
translucence or opacity of the material, we will find ourselves
cutting jasper and agate cabs from the same piece of rough.

Lee Einer