CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Fri Nov 22, 2019 1:18 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 85 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6  Next
Author Message
 Post subject:
PostPosted: Fri Jul 27, 2007 10:59 pm 
Offline
Gold Member

Joined: Mon May 14, 2007 11:00 am
Posts: 1133
Location: Monterey, CA
Correction: There are six plagioclase feldspars.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jul 28, 2007 10:04 am 
Offline
Platinum Member

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2591
Hi Bill,

That is interesting and somewhat confusing.

I was trying to get that working in my head with a mineral that is idiochromatic and that doesn't belong to a series of endmembers (like the isomorphous series). Can't seem to come up with one.

How would you define idiochromaticy for gemmology and mineralogy when offered a job at Random House?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jul 28, 2007 10:25 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 19909
Location: San Francisco
Unfortunately, I must get ready for work now :(
I would rather stay home and work on my rebuttal :wink:


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jul 28, 2007 1:53 pm 
Offline
Gemology Online Royal Princess

Joined: Mon Oct 17, 2005 10:56 am
Posts: 6462
Location: The frozen north prairie :-/
I just want to know if I was anywhere close to being correct about any of the stones 8) :lol: .

_________________
IIJA Registered Gemologist
GIA Graduate Gemologist


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jul 28, 2007 4:06 pm 
Offline
Gemology Online Übergod
User avatar

Joined: Tue Aug 01, 2006 3:24 am
Posts: 4997
Location: McDonough GA
Morning Dove wrote:
I just want to know if I was anywhere close to being correct about any of the stones 8) :lol: .


MoDo,

That's the problem. You're always "close" to being right but never quite there.

*Runs for the hills!*


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jul 28, 2007 4:51 pm 
Offline
Moderator

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2849
Location: Ho Chi Minh City, Vietnam
Quote:
That's the problem. You're always "close" to being right but never quite there.


Are you trying to imply that MoDo is a man???????????? :lol: :lol:


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jul 28, 2007 5:02 pm 
Offline
Gemology Online Royal Princess

Joined: Mon Oct 17, 2005 10:56 am
Posts: 6462
Location: The frozen north prairie :-/
:lol: Thanks, 'Nuck!

_________________
IIJA Registered Gemologist
GIA Graduate Gemologist


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jul 28, 2007 7:02 pm 
Offline
Platinum Member

Joined: Tue Nov 29, 2005 2:02 pm
Posts: 2647
Morning Dove wrote:
I just want to know if I was anywhere close to being correct about any of the stones 8) :lol: .


Hey MoDo,

I don't think Bill offered an actual answer to the original question. He offered some insight and opinion on how the terms allochromatic and idiochromatic are used or possibly abused to fit within a certain agenda.

From a gemological standpoint, I'll stand by my original answer, but, Bill's, response certainly left room for more discussion.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jul 28, 2007 7:11 pm 
Offline
Gold Member

Joined: Mon May 14, 2007 11:00 am
Posts: 1133
Location: Monterey, CA
Doos,

I believe idiochromaticy would be a noun and I would say it was the property or condition of being idiochromatic.

I think Random House's definition of the adjective “idiochromatic,” which incorporates the prefix idio- signifying “proper to one” or “peculiar” and derived from the Greek idios meaning “one, personal, private, separate, or distinct” is excellent. However, note it makes no reference in any manner to the degree, kind, or cause for this capacity to affect light—only that it does so.

I have no problems with the mineralogical definitions: “Idiochromatic - a (mineral) deriving a characteristic color from its capacity to absorb certain light rays.” and “Allochromatic - a (mineral) having no color in itself but bearing colored impurities."
I will happily leave them to the mineralogists who prefer to deal with pure species of having the composition of their "ideal chemical formula" (To them, everything else is an impurity). Most gemstones don’t fit that criterion, as what they might call “impurities” are essential components of colored gems.

For gemology, I would propose the following:

Idiochromatic - a (gemstone) deriving a characteristic color from its capacity to absorb certain light rays.

There is really no need for the term Allochromatic, as the prefix “allo” is Greek and simply means “other.” Therefore a gemstone is either idiochromatic or not. The operative word in this discussion is the word “characteristic.”

That is why a ruby is not a sapphire and sapphires are individually described by color. They have no characteristic color and are considered merely a species. Ruby, on the other hand, is a color variety. This brings us back to my original thesis:
Color varieties of allochromatic minerals are idiochromatic gemstones.
------------------------
Quote:
I was trying to get that working in my head with a mineral that is idiochromatic and that doesn't belong to a series of end members (like the isomorphous series). Can't seem to come up with one.

Have you considered the likes of Malachite, Azurite, Chryscolla
Dioptase, Turquoise, Rhodonite, and Rhodochrosite?
------------------
Quote:
I just want to know if I was anywhere close to being correct about any of the stones

My answer was "All are idiochromatic GEMSTONES."

However, if you are taking such a test out in the real world, whether your answer is going to be considered right or wrong depends upon who is grading you, what definitions are being used, and what the question is (minerals or gemstones).


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat Jul 28, 2007 8:31 pm 
Offline
Platinum Member

Joined: Tue Nov 29, 2005 2:02 pm
Posts: 2647
Quote:
My answer was "All are idiochromatic GEMSTONES."

However, if you are taking such a test out in the real world, whether your answer is going to be considered right or wrong depends upon who is grading you, what definitions are being used, and what the question is (minerals or gemstones


Then this is not a Quiz. It's a philosophical discussion on the meaning of two different words used within more than one context.

Why shouldn't there be confusion? :)


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon Jul 30, 2007 4:47 pm 
Offline
Site Admin

Joined: Thu Jan 05, 2006 4:27 pm
Posts: 1750
Quote:
However, if you are taking such a test out in the real world, whether your answer is going to be considered right or wrong depends upon who is grading you, what definitions are being used, and what the question is (minerals or gemstones).


Wise words...I think I'll stick with the Gem-A definition till I finish my diploma.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Jul 31, 2007 5:13 pm 
Offline
Platinum Member

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2591
Hi Bill,

I have been pondering about this for a few days and I still don't have it clear in my mind.
Some of my thoughts:

Corundum is allochromatic (Al2O3.. with subscripts where needed).

Sapphire is also allochromatic in the way that we are trained, but the chemical composition is not Al2O3. It is (Ti,Fe)Al2O3. I'm sure the dots don't add up there, but let's say that is the formula for simplicity.
Now the gemmological definition I was taught works, but not the way they intended as sapphire is now idiochromatic. Basically proving your point.

I asked about the idiochromatic gems that are not part of a series and you gave a few examples (rhodonite, rhodochrosite). In those gems there is no 50/50 rule, so that doesn't work very well.

Interesting to think about.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Jul 31, 2007 7:39 pm 
Offline
Platinum Member

Joined: Tue Nov 29, 2005 2:02 pm
Posts: 2647
Doos,
While you're waiting for a reply.

This is one reason I'll never be a Scientist. While science has achieved some truly remarkable accomplishments, it has also wasted an inordinate amounts of time arguing and describing useless information.

I can't think of one time in history when a mineral or gemstone transaction took place based on whether it was idiochromatic or allochromatic. I can't imagine a penalty for being correct or incorrect.

Maybe we could blow 10 million dollars on some University study to determine a universal definition that would fit every sciences prerogative.

I only say this because I like you and hate to see you in self imposed torture trying to unravel this mystery.

Some may brand me a cynic for saying this, at least by the description Jason outlined in another Quiz thread.

But, my thoughts differ from Jason as follows:

Philosophy is just a metaphor for thinking. Whether you're considered a cynic or philosopher depends solely on your audience.

I consider myself neither. Just a guy trying to separate the relevant from the irrelevant.

Everyone, feel free to impose your most stringent punishment upon me. :)


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Jul 31, 2007 9:22 pm 
Offline
Gemology Online Royal Princess

Joined: Mon Oct 17, 2005 10:56 am
Posts: 6462
Location: The frozen north prairie :-/
:smt023 I agree, JB!

_________________
IIJA Registered Gemologist
GIA Graduate Gemologist


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Jul 31, 2007 9:26 pm 
Offline
Gold Member

Joined: Mon May 14, 2007 11:00 am
Posts: 1133
Location: Monterey, CA
Doos,

Quote:
Sapphire is also allochromatic in the way that we are trained, but the chemical composition is not Al2O3. It is (Ti,Fe)Al2O3.

I question your premise. What about colorless sapphire? Who said that was the formula?

Sapphire is not an approved name of a mineral nevertheless, it can be (and is) called an allochromatic gemstone, as it is a variety of the mineral corundum which comes in any color but red—a wide variation of hue.

Now, if you accept Webster, concerning idiochromatic minerals he wrote: "... in which the color can be ascribed to an element which form an essential part of their structure. For this reason, idiochromatic minerals can show little variation in hue."

Essentially, I am arguing that the color variety "ruby" is an idiochromatic gemstone, i.e., a color variety of the allochromatic mineral corundum which must contain chromium in order to qualify as a ruby. Sapphire is not because it does not exhibit a characteristic color, therefore sapphire must be an allochromatic gemstone.

As I said, "Color varieties of allochromatic minerals are idiochromatic gemstones."
Quote:
I asked about the idiochromatic gems that are not part of a series and you gave a few examples (rhodonite, rhodochrosite). In those gems there is no 50/50 rule, so that doesn't work very well.

I don't understand the problem. They are simply idiochromatic minerals without any color varieties. They are also idiochromatic gemstones.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 85 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 4 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock