As John Donivan, I too have hesitated to join in this discussion.
However, since there are both ‘old timers’ as well as ‘newbies’ on
this forum, the latter easily confused by the terminology we may have
adapted over the years, I believe I have to at least say something!
Webster’s New World dictionary, though not an authority on geology
or gemology, says of agate: " a noun; a hard semiprecious (yuk - my
comment) stone, a variety of chalcedony, with striped or clouded
coloring." Personally I do not think much of this definition but its
useful to our discussion. Interestingly, the dictionary describes
chalcedony as ‘a precious stone’, though in the biblical sense.
The dino bone can be a stone of some worth (semi-precious??), it is
filled with the latter and usually displays minute aspects of the
last. They describe ‘agate’ as a noun. But we also use the term
’agatized’ (not in my dictionary) which is an adjective and tells us
of a process; i.e., the bone is a fossil that has ‘agatized’, meaning
it went through a similar process of reaching a chalcedony like
material…regardless what it originally was. That makes it a
metemorphic(noun) and just like the cell by cell replacement of
petrified (or fossilized) wood with silica the result is actually
’agatized wood’. It ain’t an agate…thats for sure…but it has
been agatized. Duh…is everyone now thoroughly confused?
I got the wrong end of the stick regarding what you were saying. I
realised after I posted that it was the all ducks are birds but not
all birds are ducks type scenario and you are right.
Just to add more interest to this debate, here in Alberta, Canada we
also have dino bone and petrified wood. Ours is apparently called
silicified dino bone or wood as opposed to agatized bone. I am
uncertain what exactly is the true difference as agate, quartz and
silicified all are using different forms of silica as the base
element. Here less than 10 percent of our bone is silicified and it
tends to be a blander brown color with clear spots or sometimes a
little blue. Occasionally a little yellow calcite will remain inside
the quartz.
I know that much of the agatized wood from Oregon/Washington was
formed by tree trunks being buried in volcanic ash high in silica.
Water percolating down through the compressed ash into the wood
turned it into agate, thus keeping the cell structure in place. Some
other was formed when the wood rotted away leaving just the
impression which later filled with the agate, thus leaving no rings
or cell structure but the texture of the bark remains. Wood here is
more in Igneous rock formations.
With the wood in Alberta, and maybe the bone, it was buried in mud
or bog and silica in the water replaced the wood bit by bit, also
keeping the cell structure in place. Here the wood/dino bone is in a
Sedimentary rock formation.
Are there other stones that resemble the banding of agate in the
colours shown?
Ok, folks, I think there’s a bit of hair splitting going on here.
This is standard nomenclature. “Agatized”, “Jasperized” and
“Siliconized” are, in fact, the terms that mineralogists use for
organic materials that have been partially or completely replaced by
minerals. I refer you, for example, to chapter 7 of June Culp
Zeitner’s _Gem and Lapidary materials for Cutters, Collectors, and
Jewelers
Most fossils are composed of minerals other than the original, there
are exceptions but generally that is the case.I have seen petrified
wood composed of agate, opal, limestone etc. I even have a piece
partially replaced by malachite.The opalzied logs from the northwest
are indeed opal which is what they are called. No one goes around
saying this is not opal it is petrified wood. Agate is simply a form
of silica that has replaced the original component or the spaces in
between. Does it really matter if you call it dino bone, agatized
dino bone, dino bone partially or completely replaced by agate or
just plain dino bone?
I agree 100% that fossilized dinosaur bone is NOT an agate and I see
your point.
While they may both be members of the Species Group
Cryptocrystalline Quartz and the same variety of Chalcedony and even
share the same chemical composition they are NOT the same thing.
Agates have specific growth patterns that are not shared by
fossilized dinosaur bone.
The problem comes from the term “Agatized” which implies that the
dinosaur bone has become an agate which is not the case. "Agatized"
has been used as a term describing some fossil processes for decades
and it is indeed misleading because it implies that the new material
is agate. Dinosaur bone like petrified wood becomes stone through the
process of the organic material being replaced by mineral when
mineral laden water circulated through it. This starts with the
softer parts like the marrow and vascular system. Then as the harder
calcium is broken down it is replaced by minerals. Because this
happens a different times you get the wonderful patterns that is
unique to fossilized dinosaur bone because of different mineral
compositions in the solution when the deposits are made.
The actual process is called a pseudomorphosis as it seems like the
original material has changed as in the case of metamorphic stones
when actually the original organic material has been flushed away and
replaced by mineral.
A more proper term would be to use petrified dinosaur bone. But I do
have to say that agatized dinosaur bone sounds a lot more romantic
than pseudomorphized dinosaur bone…
I have seen petrified wood composed of agate, opal, limestone etc.
I even have a piece partially replaced by malachite.
Good point. The Carico Lake mine area there have been found turquoise
clam fossils. I don’t know they’re value because once somebody finds
one they won’t let it out of their tightly closed fist.
According to Roger Pabian you need a source of silicon dioxide for
this process and that source is volcanic ash. Does that rule out
sedimentary rock? Not at all. Imagine a tropical sea with volcanic
ash raining down on it from volcanic explosions. Presto! Silicified
coral from Indonesia. Imagine a river depositing eroded ash on a
delta with driftwood. Many different scenarios will work.
One can turn a noun into a verb i.e., agate to agatize but whether it
conveys any useful is questionable.
The other name for these type of specimens is “Psuedomorphs”. is
incorrect. And what specimens are you referring to? Pseudomorph
refers to something more precise.
However, since there are both 'old timers' as well as 'newbies' on
this forum, the latter easily confused by the terminology we may
have adapted over the years, I believe I have to at least say
something!
With all due respect, please try not to patronise us “newbies”. I
(and I’m sure many others like me) am well educated and quite well
read and don’t have any trouble with the terminology used on this and
other forums. I may be new to making jewellery but I’ve read about
rocks and gems for many years as they have interested me since early
childhood. And with regards the terminology of jewellery making, I
have spent about two years reading about that now too and as such
have not been confused with such terminology either. I have a
scientific background (having earned a first class degree in
chemistry) and have also taught science at high school level so tend
to understand most terminology I come across. Having also
communicated with a fair number of other “newbies” on this forum, I
can say that every one I’ve spoken with has also been
well-informed/educated and it has just been experience in jewellery
making that we lack.
In my paleontology classes we were taught that the process by which
bone is replaced with quartz minerals is properly termed
silicification.
Agate is a very specific form of quartz, and, while the term
"agatized" is often used to describe what is properly termed
silicification, it is still incorrect. Dino bone does not become
"agatized".
Gosh, Helen, I’m really sorry if you were offended by my input!!! It
was not aimed at you…or anyone in particular. However, if you take
a
close look at Orchid, where I have been an active participant for
many years, you will find that of the 6000 or so members around the
world, whether active or simply ‘lurchers’, a fair 2/3s are just
that…‘newbies’. There is certainly no shame in that…we all
started somewhere. In fact, so you understand where I am coming from,
after nearly 40 years in this field, having written and published
magazine articles, authored numerous papers, lectured, and taught for
many years, etc, etc, there are many areas in which I am still a
’newbie’. I stand in awe at the likes of James Binnions’ knowledge of
metals, John Burgess’ undying contributions on chemistry, Wayne
Emerys’ knowledge of lapidary, Alan Revere, Charles Brain, Peter Rowe
and the list goes on and on. When these people talk…with few
exceptions, I listen and learn. Even when we disagree because, guess
what? None of us can know it all. It is too vast an ocean! Look again
at the daily messages. Every day there are basic and rudimentary
questions on various subjects. Sometimes these questions are asked
over and over and over but those of us who have the experience
continue to patiently respond and explain. That is what Orchid is all
about. If we knew the experience or knowledge level of every member
out there, things would be different. But we do not. And so the
’oldies’ will continue to advise and assist the ‘newbies’. Otherwise,
there would be little or no need for this great forum.
Once again, whilst I will not apologise for something there is no
need to apologize for…I am sorry for any offense.
Cheers, Don at the Charles Belle Studio in SOFL where simple
elegance IS fine jewelry!
I can see what the gemology/geology/paleontology experts are saying
about the process being wrongly named and can see that the
terminology that has been adopted as a generality is not correct.
However, in the case of the photographs that Elained pointed us all
in the direction of, I looked at every picture and read all the
descriptions too (you’d think I’d have better things to do!), and in
many of the cases the pictures were macro close-ups of what could
only be described as agate - ie where the voids had indeed been
filled with the quartz material in a BANDED pattern of different
colours. In the cases of those pictures you could probably say it is
agatized dinosaur bone, but to collectively call all dinosaur bone by
that name is clearly wrong as Kevin has pointed out.
Either way, I enjoyed looking at them and I’ll look at them in a new
light and perhaps get some. It was a material that didn’t interest
me previously until I saw those lovely pictures so thanks Elaine.
Silification amazes me because silica is so non-soluble. Yet I once
found a perfect snail shell in silica embedded in sandstone, about 30
miles SW of Ottawa.
I know you didn’t mean any offense and I didn’t take it personally
(more collectively) - it was just the comment about ‘newbies’ not
understanding terminology used. All the terminology used on this
forum is usually plain old English and even though I and others are
new to it, to learn any new skill, one has to read and research how
to do things before we can begin, so all that is written is clearly
understood and if not, it doesn’t take much to do a quick search for
a definition.
I was a little rash in my response and should learn to be a little
less reactive - or should that be reactionary (that’s the chemist in
me!). So I apologise for that. Orchid is a fantastic place with lots
of people offering precious and help and I too have
enjoyed being able to help a few with less experience in things I’ve
been successful with so I know what you mean.
I guess it’s my ‘newby’ paranoia but sometimes it’s easy to feel
"bullied" by some of the big chiefs and indians of the site, even
though you weren’t doing anything of the sort. Although the term
"bullied" sounds too much, I have had offlist emails from others
from time to time thanking me for standing up to the bullies on the
site so it is something that is very definitely felt by some at times
and I don’t mind making a fool of myself so tend to speak up
occasionally on such issues.
I can see what the gemology/geology/paleontology experts are
saying about the process being wrongly named and can see that the
terminology that has been adopted as a generality is not correct.
I do not see how such a conclusion can be reached.
to be agatized, does not mean to become agate.
Without repeating what already have been said about the process, I
want to mention a chrysocolla as an example. Pure, I am using term
with some hesitation, chrysocolla does not possess a crystalline
structure to be of any use as gemstone. But been exposed to elements
is become agatized, accepted term in this case. Chrysocolla is
partially replaced by quartz, and that is what gives it structure and
strength to be used as gemstone.
So it would very correct to say that gem chrysocolla is agatized
chrysocolla, even if in appearance it has nothing to do with agate.
One of the many places I lived in the past was southern New Mexico.
That is a place where you absorb geology into your skin just by
living there. Everybody knows something about it, because it’s so
obviously around you just walking around in life. Uplifted plate
formations, extinct volcanos and the aftermath of them, on and on.
There was a place we used to go that had a textbook example of a
basalt crystal formation, with a gypsum crystal cave - like a giant
geode - within about 20 feet of it, and then the hillside next to it
was loaded with fossils you could just pick up. First I learned my
ABCs, then I learned Mohs scale… Not so hard…
Agate is a very specific form of quartz, and, while the term
"agatized" is often used to describe what is properly termed
silicification, it is still incorrect. Dino bone does not become
"agatized".
I remember being told, with regard to cryptocrystaline quartz
stones, that if you can see through it, it’s agate, and if you can’t
it’s jasper. Since most dinosaur bone is opaque, shouldn’t we refer
to it as “jasperized”?
Nope, I have to disagree with you there. You could say that the
material is a cryptocrystalline quartz combined with chrysocolla.
But to really be termed an agate it needs to have the banded
structure of the fortification agates or brazilian agates.
Helen…ignore you? Sorry can’t…you are an active participant
and contributor to the overall worth of this great forum. In fact,
thanks for being that.
One thing we can all remember during our individual learning periods
is just how vast is the knowledge base in our field. And the
innovations just keep rolling in. But, especially for the beginner,
it is easy to be overcome by the vastness and innovation. So much so
that many simply feel it cannot be mastered and want to give up.
I tell all my students as they begin their adventure to remember a
saying attributed to Sir Winston Churchill and remind them of it
often that, “The secret to success is going from failure to failure
with out loosing ones’ enthusiasm”. And so it seems to go!!
Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry!