primarily as dark, reddish brown stones, the gem marketplace now
offers beautiful garnets in every color, except blue. From bright
green drusy Uvarovite, to neon orange mandarin Spessartites, to pure
spectral green Tsavorites and raspberry pink rhodolites, garnets are
available in a wide price range and many cutting styles. With
hardnesses ranging from 6.5 to 7.5, depending on the species, garnets
are reasonably durable gemstones for most jewelry uses. Main sources
include India, Madagascar, Russia, Australia, Sri Lanka and the USA.
As there no gem treatments commonly used on garnet to enhance its
color or other properties, it generally is safe to assume the stones
In the Western world,
the custom of wearing birthstone jewelry started in 18th century
Poland and has spread all over the world. Check out the Gem of
the Month Archive to read
more about many of the species/varieties mentioned below. Find the
month of your or your loved one's birthday and Search
our Catalog for gemstones
and jewelry pieces of that type.
Birthstones for English Speaking Countries and Some Modern
Long a favorite, purple
quartz, or amethyst, is available in sizes from small to huge, and in
colors from pale lilac "Rose d' France" to strongly saturated
"Siberian" purple with glints of red and/or blue. As well as faceted
stones, it is possible to find lovely amethyst cabochons, carvings
and beads. It is a durable gem (hardness = 7) for most jewelry uses.
Brazil, Uruguay and Zambia are major sources in today's market. Most
amethyst is heated to enhance its color, unless stated otherwise, you
should assume stones have been treated. The heat induced color change
March: Aquamarine/ Traditional Alternate: (Bloodstone)
Named for its
resemblance to the color of sea water, beryl in hues of blue-green to
blue in medium dark to pale tones is called aquamarine. It can be
found in a variety of cutting styles and makes a brilliant and
durable jewelry stone (hardness = 7.5). Virtually all aquamarine has
been heated to reduce green tones and produce a purer blue, a change
which is stable. Main sources are Brazil, Zambia, Madagascar and
Bloodstone is an opaque dark green jasper with red spots. The main
source is India. Like all jaspers, bloodstone is a durable, hardness
= 7, gem for most jewelry uses.
With hardness of 10 and
the brightest luster of all tranparent gemstones, diamonds have a
unique place in the gem marketplace. Diamonds occur in colorless and
near colorless forms as well as rare fancy colors. Both color
enhanced and synthetic diamonds are available as well as many diamond
simulants, chief among them being cubic zirconia. Major sources
include South Africa and Australia.
ACS suggests any colorless
natural gemstone as an alternate. Examples would be white sapphire,
white topaz, Goshenite, petalite, phenakite, Danburite, white zircon
or rock crytal quartz. Depending on the species, hardnesses vary, but
most make reasonably durable jewelry stones.
Phenakite Rock // Crystal Quartz
White Sapphire //
White Topaz //
Beryl with medium to
medium dark green color, contributed by chromium or vanadium content,
is called emerald. Although frequently visibly included, traditional
oiling treatments enhance the clarity of most pieces. With hardness
of 7.5 they make reasonably durable gemstones, oiled stones, however,
require gentle cleaning with no solvents, steam or ultrasonics. The
world's highest quality gems come from Colombia but Brazil, Zambia
and Russia also contribute stones to the marketplace.
June: Pearl--Traditional Alternates: Alexandrite,
Pearls are one of the
few gemstones of organic rather than mineral origin, and also one of
the few identified almost exclusively with one sex (female). Today's
pearls ("cultured") are joint products of mollusc and human
cooperation and can be from fresh or salt water species. Another
unique characteristic is that pearls are the only gem commonly worn
unfashioned (not cut or polished). Pearls are delicate gems that must
be worn and cleaned gently. Fresh and saltwater pearls in many
shapes, sizes and colors are available. Many different treatments
might be used to enhance a pearl's quality or change its color, so
unless otherwise stated, you should assume pearls to have been
treated. The majority of the pearls sold by ACS are
Alexandrite is color-change chrysoberyl, and one of the world's most
highly valued gem varieties. Few specimens of high quality are
available, but the best of these show a color change from raspberry
red to teal blue-green when the light source changes from
incandescent to fluorescent or daylight. Cat'seye forms occur.
Synthetics and imitations are available at more modest prices.
Alexandrite is generally untreated and makes a very durable jewelry
stone (hardness = 8.5). Although, historically associated with
Russia, today's sources are Brazil, India and Sri Lanka.
Daylight or Fluorescent
Color // Incandescent Color
Moonstone is a type of feldspar that displays an optical phenomenon
called "adularescence", a floating light over the surface, often
called "shiller. They range from transparent to opaque and occur in a
variety of colors. They are generally cut as cabochons or used for
carvings, but especially transparent pieces are sometimes faceted.
The most valuable type is colorless with strong blue shiller. Some
moonstones show a cat'seye or, rarely, a four rayed star. About as
fragile as opal (hardness = 6), they should be treated somewhat
gently. Most moonstones are unenhanced.
Red corundum is known
as ruby (while all other colors of that mineral are called sapphire).
Chromium is the coloring agent. Large fine rubies are the most
expensive gems sold in today's marketplace bringing prices
considerably above that for diamonds of the same size and quality.
The world's highest quality rubies come from Burma (Myanmar),
although Kenya, Pakistan, Vietnam, Thailand and Madagascar are
important sources as well. Ruby is a very durable jewelry gem
(hardness = 9), that has generally been heat treated. Some specimens
show a "star" effect (asterism).
Peridot occurs in
shades of limey to olivey yellowish green that are unique in the gem
world. Major sources include the USA (Arizona), Pakistan, Burma and
China. One of the minority of idiochromatic gem species, whose color is derived from its
inherent chemical compostion rather than from impurities,
(allochromatic) like most. It is a reasonably durable jewelry gem
for most applications with a hardness of 6.5. There are no treatments
commonly used to enhance peridot.
Alternate: Lapis Lazuli
thought of as blue corundum, sapphire occurs in a wide color range,
as well as in phenomenal form, as star sapphires. Currently sapphire
is the world's most popular colored gemstone with the US leading in
purchases. Sapphires, with a hardness of 9, are second only to
diamonds in durability. Most sapphires have been heated to enhance
color, but a large variety of more exotic treatments exist in the
marketplace. ACS sells only natural stones or those treated with
nothing more than simple heating.
Lapis Lazuli is a blue rock made of several different minerals with
an average hardness of about 5.5. One of the world's most
historically important gems, it's royal blue color often with specks
of golden pyrite is highly prized. An opaque stone, it is most often
used for cabochons, beads and carvings. Sources include Afghanistan
and Chile. Most true lapis is unenhanced, but synthetic lapis and
various simulants do exist in the marketplace.
Alternate: Pink Tourmaline
Opal is one of the
world's most popular and variable gemstones. It ranges in form and
color from the bright red and oranges of Mexican opal to precious
white, crystal and black opals through matrix and boulder types and
to the transparent crystal opals. Somewhat fragile, with hardness of
6, many precious opals are offered in the marketplace as doublets or
triplets. Precious opal is distinquised by a phenomenon called "color
play". This is caused by diffraction and interference of light rays
as they pass through opal's ultramicroscopic structure of tiny
stacked silica spheres. Australia, Mexico, Brazil and the USA are
major sources. Treaments to darken color and stabilize pieces are
fairly common. ACS sells only untreated opals.
Pink tourmaline has gained popularity recently, and is available from
many sources world-wide and in many shades from pale baby pink to
darker pinks tinged with reddish, brownish and orangey hues.
Tourmaline makes a durable jewelry gem (hardness = 7.5). Most
tourmaline is heat treated and a few types are irradiated, but the
colors obtained are stable.
November: Yellow Topaz--Modern Alternate: Citrine
Since the advent in the
market place, in recent decades, of heated and irradiated blue topaz,
many don't realize that, historically, the color associated with this
gem was yellow. To distinquish this color, the term "precious topaz"
is used, with "Imperial" being reserved for specimens of precious
topaz that show a particularly intense orangey to reddish color. It
is a brilliant and durable jewelry gem (hardness = 8). The major
source of yellow topaz in world commerce is Brazil. Yellow topaz is
commonly heat treated.
Citrine is yellow quartz, and although it does occur in Nature, the
majority of the richly colored pieces in today's marketplace have
been heated. Large, clean pieces are available, so this stone is
popular with custom cutters and carvers and is often available in
spectacular cuts. At hardness 7 it is a durable gem for most jewelry
applications. The major source is Brazil.
Alternate: Blue Zircon. Modern Alternates: Blue
December presents the
widest range of alternates for birthstone choices:
Turquoise is an opaque
blue to blue green gem often with black or tan matrix. Although once
associated in the US almost exclusively with Native American silver
jewelry, there has been a recent surge in interest in this gem by
modern designers working in gold. Sources include USA, Mexico and
Iran. Somewhat fragile (hardness = 6) and sensitive to exposure to
chemicals, it should be treated with care. In the gem marketplace you
will find stones that have been enhanced by various treatments that
seal the surface, fill cracks, or change color. A great variety of
synthetic and simulant gems are offered as well. ACS sells turquoise
that is unenhanced, or at most, has had a simple paraffin wax surface
Blue zircon has been heated to that attractive color from the natural
orangey brown rough. Its saturated greenish blue color and top-notch
luster and brilliance have led to recent increases in popularity and
familiarity. It is a relatively durable gem with hardness of 7.5. The
main source is Cambodia.
Within recent years blue topaz (irradiated and heated white topaz)
and Tanzanite (blue-violet heated zoisite) have been promoted as
alternatives to the traditional choices. Topaz is a durable jewelry
gem (hardness = 8), but Tanzanite is rather fragile (hardness = 6.5)
and requires gentler care. Most blue topaz originates from Brazil,
and all Tanzanite comes from Tanzania.
**If you don't especially care for the
stone(s) assigned on this list to your birth month -- never fear. By
doing some internet searching on "Mystical Birthstones" [Tibetan],
"Ayurvedic Birthstones [Indian] "or those below you have many, many
additional choices. With a little seaching anyone can find a gem that
has special meaning for them!
Here are some links for
alternates courtesy of www.gemologyonline.com:
Historical/Birth and Zodiac
Chakra Gems: http://www.gemologyonline.com/chakra.html
Anniversary Gems: http://www.gemologyonline.com/anniversary.html
Gems for Days of Week:
Official State Gems/Minerals: http://www.gemologyonline.com/official_state_gems.html