Technical Information on Gemstones
Number of Articles: 106
Advanced Gem Analysis
Gemstone identification increasingly depends on high tech instruments such as FTIR, EDXRF and LIBS
African Tsavorite Garnet
Tsavorite is a rare vivid green grossularite garnet, colored by chromium or vanadium, with deposits mainly in East Africa.
All About Gemstone Treatments - Information
Many gemstones today are treated with various methods to improve color and quality. Learn about the latest treatments and how they are detected.
Alternative Metals for Jewelry-Making
Alternative metals such as stainless steel, tungsten carbide and titanium can be used to make modern jewelry. Read more about other metals for jewelry-making
Turquoise has been an important gemstone in many cultures for thousands of years. What makes turquoise so special?
Asscher Cut Gemstones
The Asscher cut is a modified emerald cut with a square shape, cut corners and a deep pavilion. The result is greater brilliance and fire
Beryllium Treatment for Gemstones 'Be Heate...
Gemstone Treatments are nothing new, but beryllium gemstone enhancements (Be heated) to improve color is a recent innovation that has made gems more affordable, e...
Blue Topaz Gems: Learn About Blue Topaz Gem...
Blue topaz is one of the most popular colored gemstones. There are many trade names for the different shades of blue, including Swiss blue, London blue and Sky bl...
Brilliance, Luster and Fire
These are important technical terms in gemology, but they are often misused. Learn how to use these terms correctly to describe gemstones.
Aquamarine belongs to the same gem family as emerald. But aquamarine has better durability, transparency and clarity.
Many gemstone are certified to guarantee their authenticity. But not all gem certificates are created equal
Classifying Gemstones: How Gemstones Types ...
Gemstones are classified by species, groups, types and varieties; and are assigned to the 10 mineral classes. Learn more about how precious and semi-precious gems...
Color Change Fluorite Gems
Color change fluorite is a rare gem that displays a color change under different lighting conditions, often from blue in daylight to purple under incandescent light
Color Zoning in Gemstones
Color zoning refers to the uneven distribution of color within a gemstone. It is usually not desirable, but some gems are valued specifically for their color zoning
Colored Gemstone Clarity Grade Table
Clarity grading for colored gemstones is not as simple as for white diamonds, colored gemstones are categorized into 3 types, and are then graded for clarity
Concave Cut Gemstones
Concave cutting is a recent innovation that uses curved rather than flat facets, resulting in a more brilliant gem. But not everyone is impressed
Ever since the discovery of paraiba tourmaline, the market is excited about copper-bearing gems. What's so special about copper?
Cubic Zirconia Info
Cubic zirconia, a synthetic gemstone, became the most successful diamond simulant on the market
Culet in Cut Gems
The culet is the tiny facet at the very bottom of many faceted gemstones. Some gems are cut with a closed culet.
The art of cutting gems is known as lapidary. It requires a high degree of skill to produce a well polished faceted gem.
Cutting Gemstones - Gemstone Information
Cutting gemstones is known as lapidary work, and the shaping, engraving, faceting and polishing of stones is performed by a person known as a lapidary
Detecting Gem Treatments
Gem treatments should always be disclosed, but not all enhancements can be detected, even by the best gem labs
Detecting Synthetic Quartz
Synthetic quartz has become very common in the gem market. Distinguishing synthetic from natural quartz takes considerable expertise.
Diamond and Graphite
Diamond and graphite have the same chemical composition, but they are as different as could be.
Diffusion Treatment for Gemstones
Diffusion treatment of gemstones is controversial, and may affect the ability to recut the stone in the future.
Drusy Gemstone Info
Drusy (druse or druzy) refers to encrustations or clusters of minute crystals in a matrix
Natural emeralds tend to have surface-reaching fissures and are treated with oils, resins or polymers
Epidote & Unakite: Green Epidote Gemstone Info
Epidote is a silicate mineral often recognized by its pistachio green color. Unakite is a type of granite which contains epidote; both gemstones are cut en caboch...
The art of faceting enhances the brilliance and luster of gemstones. Buy faceted gemstones online at GemSelect.
Fine Iolite is Rare
Iolite gemstones with good color saturation and clarity are rare in sizes over 1 carat.
Finest Red Rhodolite Garnet
Rhodolite, the rose-red to violet-red garnet, is a mixture of almandite and pyrope. It has the best red of any garnet.
Fracture Filled Treatment - Gemstone Inform...
Fracture filling is a common enhancement for emeralds, turquoise and a number of other gemstones. Learn about fracture filling and other gem enhancements at GemSe...
Why are so many fracture-filled rubies being offered in the market? Should you buy one?
Gem Color Saturation
Color saturation, sometimes known as chroma, is a measure of the purity or intensity of color hue. Highly saturated colors are highly valued in gemstones.
Gem Pavilion, Girdle and Crown Guide
A GemSelect guide to colored gemstone anatomy, learn how to identify a gem's pavilion, girdle and crown, and about different cutting styles and why they are used
Gemstone & Mineral Glossary - Gemstone Info...
A comprehensive glossary of terms used to describe colored stones, precious and semi-precious gems, minerals and gemstone jewelry. Gemstone and Jewelry Informatio...
Gemstone Clarity Scale - Gemstone Information
GemSelect grades colored gemstones according to the following clarity scale: IF, VVS, VS, SI and I1, type 1, type 2 and type 3 should also be taken into account
Gemstone Cleavage Chart - Gemstone Information
Chart with cleavage ratings for more than 110 varieties of gemstones. Learn which gemstones have perfect cleavage and which have none at all.
Gemstone Dispersion Chart Information
Looking for gemstones with significant fire? Here is a chart that ranks many gem varieties by their dispersion or fire.
A gemstone doublet is a composite stone made up of a natural gemstone and a less expensive material. Opal doublets are commonly found in the market.
Gemstone Hardness and Durability
Hardness is only one measure of a gem stone's durability. Learn what other properties are important.
Gemstone Hardness: Durable Gemstone List an...
Gemstone Hardness explained: Mohs scale examples with Images to compare. Find a gemstone hardness chart which lists all gemstone names with hardness values. Downl...
Trying to identify gemstones has become more challenging with the advent of new treatments and synthetics. What once was an art has become a science.
The most comprehensive library of gemstone information on the internet. Info on more than 80 varieties of gemstones.
In the gem trade, gemological labs have the last word in gemstone identification. A recent lawsuit shows that might not always be true.
The names of many semi precious stones seem confusing and awkward. But accuracy of naming is extremely important in the gemstone industry.
Well-cut faceted gemstones display 3 different illumination effects: brilliance, scintillation and fire
Gemstone Shapes vs Cuts, Learn the Differen...
The distinction between gemstone shape and cut is often confusing. Round brilliant, square princess and emerald-cut are everyday terms in the gem trade.
Gemstone testers are becoming useful. But they are still no substitute for a trained gemologist.
Gemstone Trade Names
Some marketing names for gemstones have succeeded; others, thankfully, have failed.
Gemstone Treatment Disclosure
The Federal Trade Commission defines the rules for disclosing gemstone treatments. These rules may not go far enough
Gemstone Treatments: Stabilization and Impr...
Stabilization and impregnation are gemstone enhancements that improve the hardness, density, color and durability of naturally fragile gemstones, especially turqu...
Gemstones as Art
Cutting gems is a traditional craft, but a new art has developed in the last 30 years.
Gentle Heat Treatment
The term -gentle heat- for the heat treatment of sapphire and ruby is seriously misleading, and should be avoided
Green Zircon: Rare Low Metamict Natural Zir...
Green zircon, low zircon or metamict zircon, forms as a result of radiation from uranium & thorium. It is especially rare and highly prized by gemstone collectors...
Heat Treatment - Gemstone Information
Some gemstones are routinely heated to improve their color and clarity. Learn how heat treatment works and how it can be detected.
Gem-quality hemimorphite is usually blue or green, and bears some similarities to chrysocolla, smithsonite and turquoise.
History of Briolettes
The briolette, a pear-shaped gemstone with geometric facets, is one of the oldest styles of cut gems.
How Gemstones are Formed: Learn about the p...
Most gemstones form in the Earth's crust. Only two gemstones, diamond and peridot, form in the mantle. Learn about how gemstones form.
How Gemstones Get Their Colors
Some gemstones get their color from their essential chemistry; others from trace elements or impurities. Learn how the different gem varieties get their color.
Quartz can be produced in the lab using the hydrothermal method. How do you detect synthetic amethyst and citrine?
Irradiation Treatment - Gemstone Information
All about the irradiation of gemstones to improve their color.
Kyanite is an unusual gemstone because it has a highly variable hardness, depending on the direction of the crystal.
Labradorite Iridescence: Optical Phenomena ...
Labradorite is an iridescent gemstone with a fascinating metallic luster when viewed from certain angles. Iridescence is also found in a variety of other gems too...
Making Mystic Topaz and Mystic Quartz
Mystic topaz and mystic quartz are produced by placing a very thin permanent coating onto colorless topaz or quartz which causes the gemstone to display rainbow c...
Minerals, Rocks and Gems
What is the difference between a mineral, a rock and a gemstone? You'll find some answers here.
Almost all gemstones are minerals with a crystalline structure. But a few gem varieties have an organic origin.
Paraiba Tourmaline Gemstones
Paraiba tourmaline is a rare copper-bearing gemstone with an exceptional neon blue or blue-green color.
Peridot, the birthstone for August, has many unusual qualities. Unlike most gemstones, peridot is formed deep within the earth.
Pezzotottaite, a rare gem first discovered in Madagascar, is often confused with red beryl.
Pictures of Gemstones
High quality photos of thousands of gems. More than 115 gem varieties, including sapphire, ruby, emerald, tourmaline, spinel, zircon, amethyst, topaz and garnet.
Planetary gemologists prescribe gems based on astrological principles. Using the right gems is said to enhance health, wealth, power and popularity.
Some gemstones display different colors when viewed from different angles. Andalusite, iolite, kyanite, kunzite, sphene and tanzanite exhibit pleochroism to a str...
Prong Vs. Bezel Settings
Prongs and bezel settings have advantages and disadvantages. Learn about prong (or claw) settings and bezel settings for gemstone jewelry.
Scientists are using Raman spectroscopy to identify gemstones and minerals with a Star Trek-style tricorder device.
Clinohumite is a rare mineral and an especially rare gemstone. It is a member of the humite group of minerals, which includes humite, clinohumite, chondrodite, an...
Rare Sillimanite Gems
Sillimanite is a rare collector's gemstone that is colorless, grayish-white, green, bluish or brownish hues. Transparent, faceted sillimanite gems are extremely rare
Refractive Index Chart - Gemstone Information
A chart of the refractive indices for more than 115 varieties of gemstones, sorted in descending order.
Seeing Gemstone Stars - Asterism Effect Inf...
Learn how to evaluate star gemstones, and why the star may not be easy to see under diffused light. Gemstones that display the star effect, known as asterism, are...
Semi-Precious Gemstones - The Diverse World...
The world of semiprecious stones is incredibly diverse. Some are as rare and valuable as any precious stone. Others are very affordable. In between is a remarkabl...
Simulants Vs. Synthetics - Gemstones
Fake gemstones may be synthetics or simulants. Learn how to identify the difference between these.
Singly Refractive Gems
Diamond, garnet and spinel are well known as belonging to the small group of singly refractive gemstones. But there also are some lesser known members of this group
Specific Gravity Chart - Gemstone Information
Specific gravity is the term for the relative density of a gemstone. This chart shows the specific gravity for more than 60 varieties of gemstones.
Sphene is one of very few gemstones with an adamantine or diamond-like luster. Sphene's dispersion or fire even exceeds diamond.
Spodumene is species of gemstones that includes hiddenite and kunzite. Gem-quality spodumene occurs very rarely.
Star Diopside the Phenomenal Black Star of ...
Star diopside is known in the gem trade as the Black Star of India. Not as well known as chrome diopside, but special and unique with asterism chatoyancy - GemSelect
Star sapphire and star ruby are examples of gems that exhibit asterism or the star effect. Learn why some gemstones exhbit this rare phenomenon.
Synthetic Emerald - Carroll Chatham and Lab...
Synthetic or created emeralds were first made commercially successful by the American chemist Carroll Chatham
Synthetic Moissanite - Diamond Substitute ...
Moissanite is the latest diamond simulant to hit the market, with a hardness and density more diamond-like than cubic zirconia
Synthetic Ruby and Sapphire - Flame Fusion ...
In 1902 the French chemist Verneuil invented the flame fusion method for creating synthetic corundum. It is still being used today.
Taaffeite Gemstones - Rare Gemstone Varieties
Taaffeite is one of the rarest gem varieties in the world. It has many similarities to spinel, but is doubly refractive
Tension settings use compression to hold a gemstone in place. The designs are stunning, but are these setting secure?
The Mystery of Andesine-Labradorite
An attractive red feldspar called andesine has attracted a lot of attention in the gems world. What is really known about andesine?
The Secret of Spinel Gemstones
Spinel is a gemstone that is not well known in the commercial jewelery world, but one which has become a great favorite with gem dealers and gem collectors. Learn...
The World of Quartz Gemstones
Quartz is a very common mineral but the quartz family is incredibly diverse and endlessly fascinating.
Understanding Gemstone Cleavage
Some gemstones, including diamond, topaz, tanzanite and fluorite, have perfect cleavage. Learn about why this is important.
Untreated Gems for Jewelry - Part II
There are many untreated colored gemstones that come from the mines to the market completely natural and unenhanced, such as opal, tourmaline, quartz, spinel and ...
Some varieties of gemstones are never treated, and they represent exceptional value in today's gem market.
Uvarovite Garnet - Rarest of all garnets
Uvarovite is the rarest of all the garnets, and is rarely found in gemstone quality. Uvarovite drusy from the Ural mountains is an outstanding emerald green
Valuable Gemstone Inclusions
Conventional wisdom about colored gemstone inclusions is that less is more. But some inclusions are valuable.
What is a Natural Sapphire?
Natural sapphires are mined from the earth; synthetic sapphires are produced in a lab. But are natural sapphires enhanced by humans still natural?
What's Special about Spessartite?
Spessartite is no ordinary garnet. With its striking mandarin orange color and its high refractive index, it is one of the finest gems in today's market.
Why are Some Gems Cut as Cabochons?
What are gemstone cabochons, and why are some gemstones cut as cabochons and others as faceted gems?
Zircon and Zirconology - The Study of Zircon
Zircon is the oldest mineral on Earth, over 4.4 billion years old. It is also a fine gemstone with great brilliance and fire.
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Note: 1ct = 0.2g