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Q: test for genuine coral bead ( Answered 5 out of 5 stars,   2 Comments )
Subject: test for genuine coral bead
Category: Science
Asked by: lucia4-ga
List Price: $25.00
Posted: 04 Aug 2005 13:56 PDT
Expires: 03 Sep 2005 13:56 PDT
Question ID: 551783
Is there a test to tell whether a coral bead is really genine coral
rather than glass? I have inherited some coral jewelry, and also
bought some in second hand shops.  I'm particularly interested in a
way to test bead--not the more irregularly shaped branch pieces. And
all colors from pale pink to a darker red. I would, of course, prefer
a non-destructive test. How can dealers and sellers be so confident in
assuring you that their piece is "genuine coral"?
Subject: Re: test for genuine coral bead
Answered By: nenna-ga on 04 Aug 2005 14:55 PDT
Rated:5 out of 5 stars
Good afternoon lucia4 an thank you for the question.  I hope you find
the following information useful.

Coral used in jewelry making ranges in color from pale pink (called
angelskin coral) to orange to red to white to black. The most valued
colors are deep red (called noble coral) and pink.

Red Coral: The most valued coral of all, favored worldwide for its
hardness, beauty, and sanguine hue. Red Coral is brought up from the
sandy bottom of the Mediterranean, and the Gulf of Naples near Genoa.
It is also found off Algiers and Tunis on the African side, in the
waters of Sardinia, Corsica, Catalonia and Provence, as well as along
parts of the French and the Spanish seaboard.

Precious, or Noble Coral: A type of red coral called Corallium Rubrum,
or Corallium Nobile, Precious coral can be found in the Mediterranean,
Sardinia and Sicily, as well as in Tunis, Algeria and Morocco.

Black Coral: This coral is a horny substance particularly good for
carving and molding ? it actually bends when it is warmed! The black
hue is believed to be coral in the first stage of decay, since the
color only persists a little below the surface. Once abundant in the
Persian Gulf, a similar type is found in the Mediterranean.

Blue Coral: As with Black Coral, this variety is thought to be coral
in the first stage of decomposition, since the color usually extends
only just below the surface. It is known both as Allopora Subviolacea
and Akori. This unusual variety has been found off of Cameroon.

Golden coral: Divers off Maui, in Hawaii, have brought up this pretty
variety of coral, which has a resinous or lacquered texture.

It used to be thought that coral protected the wearer, so it was a
traditional gift to children.

Since it is composed of calcium carbonate, coral will effervesce
(fizz, bubble or spark) if touched with acid.   I believe you can
effectively ?test? your coral jewelry using this method but if you
insist on doing it yourself, be very careful as we all know that acid
can be very harmful if it comes in contact with skin or other things.
Coral is also porous so there will be some "imperfections" in the
coral beads.  Coral is also softer than glass and other gem materials
with a hardness of only 3.5. As a result it should be stored carefully
to avoid scratches.

Although your jewelry could be genuine, to be sure you really need to
get a professional evaluation by a certified jewelry appraiser.  I can
give you a list of appraisers in your area if you tell me the city &
state you live in.  Otherwise, you may want to use the Superpages
database found at:

( )

If this answer requires further explanation, please request
clarification before rating it, and I'll be happy to look into this

Google Answers Researcher

Jewelry & Gem Dictionary
( )
( )

Clarification of Answer by nenna-ga on 04 Aug 2005 15:47 PDT
I apologize for not mentioning this in my answer but I have contatced
a local jewelry appraiser in my area for more information on how to
tell genuine coral from fake glass coral and expect a reply back some
time tomorrow.  Once I hear back from him, I will post an additional
clarification for you.



Request for Answer Clarification by lucia4-ga on 04 Aug 2005 15:57 PDT
Thanks--that was a lot of good information.  You mention that, since
coral is calcium carbonate, it will fizz when touched with acid.  What
kind of acid? Is household vinegar strong enough (if placed, for
example, in the drilled hole)?   You have advanced my quest
considerably and I will rate your answer highly after we complete this
clarification dialogue.  Thanks!

Clarification of Answer by nenna-ga on 04 Aug 2005 16:17 PDT
If I remember by chemistry correctly,  calcium carbonate reacts with
acids to produce carbon dioxide gas, which we observe as bubbles. It
can be tested using regular household vinegar.

According to most chemistry sites on the net, the "acid test" the
geologists use to test minerals uses either dilute hydrochloric acid
(<10% solution) or dilute acetic acid (vinegar).

Additionally, Nancy Stacy, a certified jewelry appraiser based in
Walnut Creek, CA, has verified that the methods mentioned above would
be used by a gemologist to test if the coral was genuine or not. 
Additionally, they could take a Refractive Index reading, and with
microscopic could observe growth lines, small pits and areas of
branching.  If you have any other questions for her, you can email her


lucia4-ga rated this answer:5 out of 5 stars and gave an additional tip of: $5.00
You exactly addressed my question and gave me useful information, plus
many additional facts that I was glad to know.  Well worth the money! 
Very prompt answer and phrased in exact language that was clear and
easy to understand.  Thanks!

Subject: Re: test for genuine coral bead
From: nenna-ga on 04 Aug 2005 17:21 PDT
Thank you very  much for the rating and tip.  I am very pleased to
have been able to help you.  If you need anything else, please do not
hesitate to ask!

Subject: Re: test for genuine coral bead
From: nenna-ga on 05 Aug 2005 06:31 PDT
I received back some additional information and though I do not think
it pertains to the jewelry you have (you stated you have colors from
pale pink to darker red) I wanted to give you the information anyhow. 
I was told by another jewelry appraiser, Lindy Matula
[], the golden and black varieties of coral,
being horny types, do NOT react as the calcareous corals do with acid.



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