Anniversary gemstones:  While less well-known than the birthstones associations, the major US jewelry and gemstone associations have agreed on the following list as a helpful guide for selecting anniversary gifts.

Birthstones:   The assignment of gemstones to birth months has been a popular lore from at least the first century.  The associations have changed over the years, but in 1952 the following list was adopted by the major jewelry associations.  See information below the chart for photos and descriptions of the birthstones.

Cameo:  A carved shell in which the upper layers have been cut away so that the carved figure contrasts against the darker inner layers of the shell.  The shell "Cassis Rufa", known as Cornelian, is found off East Africa and has a reddish-brown interior.  "Cassis Madagascariensis", which has a darker brown interior, is found in the Bahamas.  Cameos are also made from other materials, such as Agate, Jade and Ivory.

Gemstones:  Following is a useful survey of the gemstones you might find in jewelry here at the Christian Jewelry Shop.  There are, of course, many hundreds of gemstones, so these only represent a few of them!  Each stone is illustrated with the more commonly available colors (because many are available in multiple colors), with facts as to their geological origins, hardness (1 to 10 (hardest) on the Moh's scale) and relative weight (by specific gravity).  Please note that most natural gemstones, such as pearls, emeralds and rubies, contain natural inclusions and variations in color which are not seen in artificial stones.  These imperfections are the marks of their natural origin, and are typically more noticeable than in diamonds. Just because an emerald, for instance, is "natural", it does not necessarily mean that it is desirable--a highly flawed stone is simply ugly, no matter what its pedigree!   For this reason, many of the rarer gemstones are available today in Lab Created, or synthetic, form--these are actually grown in a laboratory environment and are the same chemical composition as natural stones, except that they are virtually flawless.  Lab Created is NOT the same as "imitation" gemstones, which are not the same chemical composition as the genuine gemstone.  And, even natural gemstones are routinely treated (with heat, radiation or chemicals) to enhance color or to reduce imperfections.  We offer jewelry with both Lab Created (synthetic) and quality natural stones--synthetic stones are always indicated in the product description. 

	Alexandrite: Rare, color-changing gemstone which appears grass green in daylight and raspberry red in artificial light, some with "cat's-eye" effect.  Available as synthetic.  Composition: beryllium aluminum oxide; hardness: 8.5.
	Agate: Translucent, cryptocrystalline variety of quartz--a banded variety of chalcedony.  In addition to banded varieties, "feathered", "mossy" and "plumed" varieties are common.
	Amethyst: Transparent purple quartz, available in shades from light to dark purple, is also the February birthstone.  Available as synthetic.  Keep from high heat and strong direct sunlight.  Composition: silicon dioxide, hardness: 7.0.
	Aquamarine: Member of beryl family, as is emerald, ranges from light blue to bluish green to deep blue and is the March birthstone.  Is commonly available in excellent clarity, unlike emerald.  Composition: beryllium aluminum silicate; hardness: 7.7.
	Citrine:  From the quartz family, ranges from lemon yellow to brownish amber, a plentiful gemstone, it is often made by heating pale amethyst. Composition: Silicon dioxide; hardness: 7.0.
	Cubic Zirconia: Rare in natural occurrence, CZ has been synthetically produced in volume and multiple colors since the 1970's.  To the untrained eye, white CZ appears as a high-quality diamond, though it is 75% heavier, has more "fire" and is softer than diamond.  Composition:  zirconium oxide; hardness: 8.5.
	Diamond: The king of gemstones, we list it here simply for comparison.  Diamond is pure carbon, with included imperfections of other captured minerals, and is the April birthstone.  Available as synthetic.  Composition: carbon; hardness: 10.
	Emerald:  One of the "precious gems", emerald is a member of the beryl family, very rare, and is the May birthstone.  Natural emeralds contain more inclusions and other flaws than most gems, tolerated because of its rarity.  Often oiled to hide flaws, should never be ultrasonically cleaned.  Available as synthetic.  Composition: beryllium aluminum silicate; hardness: 7.7.
	Garnet:  Available in almost any color range (greens (see Tsavorite), reds, yellows, oranges, color-changing), but most commonly seen it its deep red variety, some of which can be mistaken for ruby.  Rhodolite is raspberry to deep pinkish red, while Mozambique is slightly redder and darker.  January birthstone.  Composition: magnesium aluminum and iron aluminum silicate; hardness: 7.
	Iolite: Transparent, deep blue to yellowish-gray, also called dichroite or cordierite, similar in color to sapphire but not as hard, relatively new to jewelry. Composition: magnesium aluminum silicate; hardness 7.3.
	Jade:  Two distinct minerals are both called Jade: jadeite (most valuable) and nephrite.  Jadeite is found in a wide range of colors--green, white/gray, mottled green/white, pink, brown, mauve, yellow, orange and lilac.  Nephrite jade is found in shades of green, from very dark (black jade) to pale.  Jadeite composition: sodium aluminum silicate; hardness: 7.0.  Nephrite composition: calcium magnesium iron silicate; hardness: 6.5.
	Onyx:  Straight-banded, semitranslucent to opaque quartz, available in reds, oranges, apricot, and browns--curved banded varieties are known as agate.  Composition: silicon dioxide; hardness: 7.0
	Opal: Unique among gems, the October birthstone, it exhibits an intense display of many colors, flashing like thousands of miniature rainbows, due to light interference from included silica spheres.  Must be treated with care, avoid heat because some opals tend to dry out and crack, periodically soak in water for several hours.  Composition: hydrated silica gel; hardness: 5.5-6.5.
	Peridot:  Yellowish green to deep chartreuse, the August birthstone, peridot can chip and scratch easily.  It is not routinely treated for enhancement.  Composition: magnesium iron silicate; hardness: 6.5-7.0.
	Ruby: One of the "precious gems", ruby is the brilliant transparent red variety of the mineral corundum, it is the July birthstone and the "gem of gems", ranging from purple/blue-red to yellowish red.  Also seen in translucent varieties with optical star effects.  Available in synthetics.  Composition: aluminum oxide; hardness: 9.0.
	Sapphire: One of the "precious gems", sapphire is a variety of corundum, occurring in virtually every color--its red variety is known as the ruby.  Blue sapphire is the September birthstone.  Also seen in a translucent "star-effect" variety.  Available as synthetic.  Composition: aluminum oxide; hardness: 9.0
	Tanzanite:  A modern gemstone (since 1967), also known as Zoisite, it is transparent blue to purple blue.  Should be protected as it can chip easily.  Composition: calcium aluminum hydroxysilicate; hardness: 6.5.
	Topaz:  This brilliant and heavy stone is often imitated with lesser value quartz (citrine), but genuine topaz is rare--it is the birthstone for November.  Topaz occurs in yellow thru orange-or pink-brown, as well as light red and the popular light to medium blue.  Composition: aluminum fluorohydroxysilicate; hardness: 8.0.
	Tourmaline:  A more recent gemstone, it is found in virtually every color, even within the same stone, though green is the most common.  Composition: complex borosilicate; hardness: 7-7.5.
	Tsavorite:  Green garnet, more durable and vibrant than emerald, yet less costly.  Also appears as rarer demantoid garnet which is slightly softer with more brilliance.  Composition: calcium aluminum silicate; hardness: 7.
	Zircon:  A natural gemstone (not to be confused with cubic zirconia, CZ), zircon is a brilliant, transparent stone occurring as colorless to brown, yellow, orange, red, green and the popular blue.  It is somewhat brittle and prone to chipping, but exhibits "fire" similar to diamond.  Composition: zirconium silicate; hardness: 6.5-7.5.

Gemstone Shape:  As gemstones in their natural state are rather shapeless, their beauty is greatly enhanced by cutting them into geometrical shapes, most of which provide numerous facets to reflect light that enters the stone back out to the eye.  The efficiency of the stone in reflecting this light is based in large part on the shape of the facets and the accuracy of their cut.  The more popular shapes are shown below, illustrated with diamonds:

	Round		Heart		Triangle Trillion Trilliant
	Emerald		Pear		Marquis
	Princess		Straight / Tapered baguette		Asscher
	Oval		Cushion		Briolette

The Round shape is found in many different facet cuts.  Smaller stones are often Single Cut, a simple cut with 17 facets (table, 8 bezel and 8 pavilion).  A Step Cut refers to a four-sided faceted cut in which the facets descend in "steps" from the table, such as in an emerald or baguette shape--the corners may be removed for more brittle gems, which adds four additional sides.  Gemstones other than diamonds are often cut as Cabochons, a smooth, facetless cut which usually takes the form of a polished dome or "sugarloaf" shape.  Gemstones which possess unusual internal optical effects, such as the star sapphire or the moonstone, are often cut in this manner.

Pearls:  June birthstone. A pearl begins its life as a tiny impurity (such as a small sea animal or grain of sand) inside the folds of an oyster's or mollusk's fleshy body.  Because it is an irritant to the animal, it is slowly coated with a hard substance, called nacre, which builds up in layers over time, forming a finished pearl.  In a cultured pearl, the irritant is placed there by the pearl farmer; in a natural pearl (extremely rare), the irritant occurs naturally.  Thus, both cultured and natural pearls are genuine pearls!  We do not offer imitation pearl jewelry.  Mother of Pearl is the nacre which lines the inside of the oyster or mollusk shell, and is often used in jewelry and jewelry boxes.  For more information about pearls, visit the Cultured Pearl Information Center (www.pearlinfo.com) or the Cultured Pearl Association of America (www.cpaa.org) websites.

Since all genuine pearls are grown over time by the oyster, they will vary in shape, luster and color.  Because of this, there have developed over the centuries terminology to quantify a pearl's characteristics.  These are not always consistent from one source to the next.  We use the following descriptions for our pearl jewelry:

Pearl grades:  The quality of a pearl is determined by its Lustre (reflectivity and depth of shine) and Surface (smoothness vs. pits/blemishes on surface).  Some pearl suppliers use "A", "B" and "C" grades, where "A" represents the highest lustre and/or the highest surface quality.  Thus, a pearl rated "AA" would have high lustre and surface quality.  Others may use terms such as "very good" to represent "A", "good" to represent "B", and so on.  Shape, color and size of pearls are not factors of quality and are quantified separately.

Pearl Strands:  When considering purchase of a pearl strand, look for knots or knotted beads between the pearls--this assures that the pearls are not lost if the strand breaks, and also prevents friction wear between adjacent pearls.  The clasp should be secure and designed to stay closed under the weight of the strand.  Some strands are elastic, and are thus lacking knots or a clasp. For information on strand lengths, see below:

Pearl types:

Akoya Cultured:  The most lustrous of all pearls, they have historically been grown in Japan, though China is now producing quality pearls of this type in sizes below 8mm (at considerably lower cost).
Freshwater Cultured:  Grown in fresh, rather than salt, water, these pearls are less lustrous than saltwater varieties, but are popular because of their variety of shapes and colors. More than one pearl may be grown in each oyster/mollusk. Sources: Japan, China, USA.
South Sea Cultured:  Grown in large tropical oysters, these pearls are relatively rare and of large size (10 to 20mm).  Consequently, they command higher prices.  Sources: Australia, Myanmar, Indonesia, Philippines.
Tahitian Cultured:  Uniquely large-sized and dark-colored (light grey to black, green, purple), these pearls command high prices and are primarily grown in French Polynesia.

Pearl shapes: 

Baroque:  A pearl shape that is not round, oval or button--any odd, misshapen shape.  If lustre and surface are good, these shapes are desirable because of their variety.
Button: Freshwater cultured pearl that is not round, but flatter in shape, with an oval cross-section.  Used on rings and earrings where a lower profile pearl is desired.
Circlé:  Any pearl which possesses an indentation surrounding the pearl as a latitude line on a globe--it may be centered, as the equator, or located toward the "pole" of the pearl.
Mabe:  Hemispherical cultured pearl grown on the inside shell rather than within the flesh of the oyster.  This pearl is used in rings and earrings where its flat back is not visible because it is attached to the jewelry piece.  Sources: Japan, Indonesia, French Polynesia, Australia.
Round:  The traditional and most sought-after shape, it commands the highest price.
Roundel:  Almost round, but slightly flattened.  Similar to button, but not as flat.

Pearl Sizes:  Pearls are sized by measuring their diameter.  Pearls above 9-10mm are much more rare and thus more costly than smaller sizes.

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