Article: Identifying
Stones
One of the most interesting and challenging questions
a retailer of semi-precious gems is confronted with is "what
stone is this?"
Often the answer is an easy one, either because the stone was ordered
specifically by specimen or because it is an easily identifiable species
of a particular mineral. For example amethyst
is easy to identify because of its purple coloring and relative transparency.
But what about
that silver ring with the unusual and beautiful stone you got as
part of an assortment from Whirled
Planet? Being able to determine the correct stone classification
will make the sale easier and will enhance the purchase from the
customer's perspective. Most people learn to identify stones through
experience. Familiarity with stone types breeds confidence and a
working knowledge that can be added to gradually over time.
Some background
information is helpful however. Gemologists use several methods
to determine a stone type. First and foremost they use primary color
as a reference point. Some minerals like azurite
or malachite
are very consistent in color from specimen to specimen. Other gems
like quartz are harder to classify because they come in all colors,
depending on what trace minerals are present. Purple amethyst is
a kind of quartz with iron present, while rose quartz gets its color
from titanium.
Color can also
be altered, as it has for millennia, to improve or change the appearance
of a stone. Most commercial citrine
is actually heated amethyst. In this same category of classification
method we can apply the idea of "grain" or texture. The
banding found in various agates, or the crystalline nature of various
quartz colors lends a certain character to each that is consistent
over various colors. The similarities between rainbow
moonstone and labradorite
are an easily identifiable example of similar feldspars that have
completely different primary color.
Gemologists
also refer to "streak color" as a means of determining
species. Basically, this involves scratching the stone with moderate
force on unglazed porcelain as found on the bottom of a dinner plate
or floor tile. The color of the streak on the ceramic shows the
true color of the stone minus the impurities that cause the coloration.
Blue
sodalite, for example, will scratch white. This test is used
for testing stone rough and will damage set stones, so don't try
this with anything you plan to sell! I mention it here for reference
purposes only.
Another method
gemologists use to classify gems is by testing their hardness. In
the 1800's the Moh's hardness scale was developed to stratify all
the gems of the world along a scale from one to ten. In practice,
the softest stone is talc,
with a hardness of one. The hardest stone is diamond, with a rating
of ten. A stone of higher hardness will scratch a stone of lesser
number on the scale. Quartz, with a hardness of 7, will scratch
hematite with a hardness of 4. While you should not try to perform
this test on jewelry set in finished form, it is a good idea to
know relative harnesses to avoid damaging your inventory.
Quartzes, agates
and jaspers are all relatively hard stones (Moh's 6-7), but rhodocrosite
(hardness 4, second
from right in picture), malachite
(3.5 - 4) and fluorite
(4) are all stones that should be stored and worn with care.
Beyond these
criteria, gemologists may also use density, transparency, refraction,
spectral analysis, and fluorescence to unlock a stone's identity.
For everyday examination, these methods are beyond the grasp of
most of us stone aficionados. We tend to rely on our experience
and "go with the gut" when making a questionable identification.
Often we will find a customer who knows a particular stone at sight,
while just as often a customer will claim to "know a lot about
stones" only to mispronounce labradorite
or misidentify sodalite
as lapis.
Ultimately it
can be very difficult to identify a stone based on the small sample
set in a pendant or ring. A particular specimen may not be representational
of the rest of its family and can thus be difficult to classify.
What I do is look at the details of the stone, including its color,
grain, inclusional qualities and its overall character, then try
to cross reference those pieces of the puzzle mentally with what
I know about gemstones from past experience. Obviously the more
you know, the better you will get at identifying those hard to classify
stones.
If I think they
are jasper
or agate,
I will give the identification with the caveat that I am not 100%
sure. I know from my own experience with the products we sell on
our site that most unknowns are either agate or jasper, but this
rule may not apply to other vendors' merchandise.
When we ship
out our pendants
or rings
by the gram, one of the best ways to order is as an assortment.
If you definitely need tiger eye or carnelian (for example), then
by all means order by stone. When you order assorted stones, you
will almost always get some unusual and exciting stone that you
have no idea how to identify. As a rule, we ship these assortments
with the following stones:
amethyst, rose
quartz, carnelian, onyx, rainbow moonstone, labradorite, sodalite,
lapis lazuli, snowflake obsidian, amazonite, dendritic agate, malachite,
nephrite jade, chrysocolla, mother of pearl, abalone, rhodonite,
rhodocrosite, tiger eye, fluorite, ruby zoisite, assorted jaspers
and agates.
This is a partial
list. There are many other stones that we get only a few pieces
here and there. If you are having trouble identifying stones, there
are several good resources I can recommend. Some good websites are:
http://www.jewelrymall.com/stones/,
http://mineral.galleries.com/minerals/gemstone/class.htm,
http://www.minerals.net.
A great book
I use all the time is Gemstones of the World by Walter Schumann.
It has over 1500 photos and lots of great background. You can buy
it http://amazon.com.
If you ever
need help identifying a stone or have questions about something
you bought from us, don't hesitate to give us a call at 888-408-0072
(808-822-2335 international callers), or drop me an email.
I'll always do me best to answer your question in a timely manner.
Highlights
of the Site
New
Arrivals section features more than 50 new items.
Many styles of regular merchandise now marked down 20%. Click here
for a smattering of examples.
No
border saris back by popular demand.
According to
the surveys we had our customers fill out last month, many people
said they wanted to see more "new merchandise." Others
said they like to see sale items. We've got both bases covered this
month with our new arrivals and our permanent price reductions on
many of our regularly stocked designs.
Look for new
purses in April, along with more jewelry and textile products. Thanks
to everyone that completed our survey in March. We are tabulating
the results and you can bet that we will respond to your input.
Last month it
was arctic here on Kauai: the temperature dipped down into the low
50's at night! Here's hoping it warms up wherever you are this month...
Aloha,
Mike McGinnis
Whirled Planet
808-822-2335 tel.
888-408-0072 toll free (US only)
http://indiasilver.com/index.asp
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