Gemstone information about prescious gemstones semi prescious gemstones

Birthstones

Ancient & Modern

MONTH	MODERN	ANCIENT
January	Garnet	Garnet
February	Amethyst	Amethyst
March	Aquamarine	Bloodstone
April	Diamond	Diamond
May	Emerald	Emerald
June	Alexandrite	Pearl
July	Ruby	Ruby
August	Peridot	Sardonyx
September	Sapphire	Sapphire
October	Rose Zircon	Tourmaline or Opal
November	Golden Topaz	Topaz
December	Blue Zircon	Turquoise or Lapis

Gem Facts

Early in this century jewelers got together and created a new list of birthstones. In the modern list you will find only transparent gems. This makes it much easier to create a mothers ring. Imagine if you needed a pearl, a cabochon of turquoise, a diamond and an emerald. This would be an awkward thing to make look nice.
Another interesting point is the addition of alexandrite. This is an incredibly rare gem and not readily available.
The ancient list is still used considerably. Many people mix the two as they feel best. This is acceptable, the modern list has not replaced the ancient one, but supplemented it.

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Gems

GEMOLOGY Gemology is the study of gemstones: what constitutes a gem, the terminology of gemstones, their physical and optical properties, and how those properties are used to identify gems. Learning gemology does not have to cost thousands of dollars. As an IGS member, you are automatically enrolled in our gemology course. The only other charges are for testing. To learn about our Gemology Course follow this link. Learn Gemology, Gem Identification

GEM IDENTIFICATION Knowing how to distinguish ruby from garnet, or diamond from CZ is an essential skill for anyone dealing with gemstones.

GEMSTONE GRADING
Another important aspect of gemology is learning how gems are graded. Grading expertise and knowing current prices, are required for successful trading and appraising.

Bead and Necklace Charts

Beads per Inch

Bead Size	Beads per Inch	Beads per 16”	Beads per 24”
2 mm	12.5	200	300
3 mm	8.3	133	200
4 mm	6.25	100	150
5 mm	5	80	120
6 mm	4.2	66	99
7 mm	3.6	57	86
8 mm	3.13	50	75
10 mm	2.5	40	60
12 mm	2.1	33	50

Cord Conversion Chart

Silk is the traditional beading cord. Its strength and flexibility are unmatched for any other material its size. Nylon and polyester cords are replacing silk. They have nearly the same strength and a longer life.

Silk	A	B	C	D	E	F	FF
Nylon	1	1.5	2	3	4	5	8

Necklace Lengths

Choker	14 to 16 inches, falls to hollow of neck
Princess	18 inches
Matinee	20 to 24 inches, falls to the crown of the bust
Opera	28 to 32 inches
Rope	Anything more than 32 inches

Diamond Look Alike Comparison Chart
One of the biggest challenges for a new gemologist is separating diamonds from their look alikes. The keys to identifying these gems are specific gravity and birefringence.
... The following stones are arranged by specific gravity. Note that there are only three pairs of stones that share the same specific gravity, (the ones in red.) In each case, one is doubly refractive and the other is not. This makes the separations simple.

Material	SG high	SG low	Birefringence
GGG GARNET	7.09	6.95	None
CUBIC ZIRCONIA	6.00	5.34	none
RUTILE	5.60	4.20	.287
ZIRCON	4.80	3.90	.000 - .059
YAG GARNET	4.60	4.50	None
SPHENE	3.55	3.45	.100 - .192
DIAMOND	3.53	3.51	None
MOISANITE	3.20	3.17	.043

It appears that zircon, which is occasionally isometric, could be confused with YAG. However, anytime zircon becomes singly refractive, the specific gravity drops below that of YAG.

MONTH

MODERN

ANCIENT

Silk

Nylon

Choker

Princess

Matinee

Opera

Rope