An Introduction to Gemology

The basic building blocks of understanding the science of gemstones.

An Introduction to Gemology

  • introduction to gemology - jewelers
    An Introduction To Gemology

    Step 1: Introduction to Gemology Lesson 1 Back to syllabus Gemology is the scientific study of gemstones. Although there may be investors and collectors who are only interested in the monetary value of gems, they’ll need a…

  • Yugawaralite
    Gem Species and Gem Varieties

    What is a Gem Species? A species is a type of mineral. A few gems, like amber and pearls, have their origins in the vegetable kingdom. However, most gems are minerals (in fact, over 140 minerals have been utilized as gemstones). Minerals are…

  • Crystalized Topaz and Quartz
    Gem Formation: How are Gemstones Created?

    An explanation of how gems are formed, and how and why gem quality crystals grow and change in nature.

  • Diamond - gemstone hardness
    Gemstone Hardness and Wearability

    By scientific definition, hardness is the ability to resist scratching” and nothing more. Ask most folks and they will tell you that feathers are soft and glass is hard. In the world of gemology though, glass is fairly soft. It can be easily scratched by a variety of what we consider to be hard substances.

  • Teardrop turquoise - gem cutting terms
    Guide to Gem Cutting Terms

    Lapidary is the art of working in stone. For some reason though, it is only applied to working with small gem materials and is not extended to large objects, like Michelangelo’s statues.

  • gem classification - synthetic
    A Guide to Gem Classification

    There is not one way to classify gems, rather there are several ways, each of which has its own purpose and its own exceptions that warrant close attention.

  • Oval Ruby - gem identification
    An Introduction To Gem Identification

    Step 1: Introduction to Gemology Lesson 8 Back to syllabus People often ask me about gem identification. More specifically, they ask me to identify their gems. Some think I can do this simply by looking at the gemstones….

  • Sulfur - crystal systems
    What are Crystal Systems and Mineral Habits?

    Step 1: Introduction to Gemology Lesson 7 Back to syllabus In crystallography, mineral habits refer to the way crystals form within a specific mineral. In the article, “How Gems Are Classified,” I mentioned that, at the…

  • One of most well known varieties of synthetic gemstones, cubic zirconia may look like a diamond but has a distinct chemistry and physical structure.  “Synthetic Cubic Zirconia” by Mauro Cateb is licensed under CC By 2.0
    Understanding Gem Synthetics, Treatments, And Imitations, Part 1: An Introduction

    Editor’s Note: Synthetic gemstones have been on the marketplace for over a century. Today, however, technological innovations and economic forces behoove gem buyers to gain a basic understanding of the science of gemstones and gem formation. This…

  • August Verneuil used a device like the one depicted here to synthesize rubies in the late 19th century. The principles behind the Verneuil technique are still used in modern crystal growth technology.  “Verneuil Torch Sketch.” Public Domain.
    Understanding Gem Synthetics, Treatments, And Imitations, Part 2: Crystal Growth

    Editor’s Note: Gemstones can be artificially created in laboratories using any one of several possible crystal growth methods. This five-part series of articles, “Understanding Gem Synthetics, Treatments, and Imitations,” is a chapter from Dr….

  • Caption: This synthetic diamond was created through the CVD (Chemical Vapor Disposition) process.  “Diamond Age” by Steve Jurvetson is licensed under CC By 2.0
    Understanding Gem Synthetics, Treatments, And Imitations, Part 3: Synthetic Diamond

    Editor’s Note: The earliest laboratory methods for creating synthetic diamond were cost prohibitive. Technological advances, however, have made it easier for synthetic diamond to enter the marketplace. Unfortunately for consumers, proper diamond…

  • Rubies and sapphires are varieties of corundum.  Our synthetic gemstone guide explains how they are created in laboratories.  “Corundum synthetic, melting bulbs – Exposed in the Mineralogical Museum, Bonn, Germany” by Ra’ike is licensed under CC By-SA 3.0
    Understanding Gem Synthetics, Treatments, And Imitations, Part 4: Synthetic Gemstone Guide

    Editor’s Note: Many gemstones can be created in the laboratory and have a longer manufacturing history than diamond. This synthetic gemstone guide covers rubies, sapphires, emeralds, opals, and many more species and explains their fabrication…

  • “Topaz with Irradiated Fragment - Smithsonian Museum of Natural History - 2012-05-17” by Tim Evanson is licensed under CC By-SA 2.0
    Understanding Gem Synthetics, Treatments, And Imitations, Part 5: Identifying Gemstone Treatments

    Editor’s Note: Identifying gemstone treatments is a challenging task even for an experienced gemologist. Below you’ll find a review of various gemstone manufacturing techniques and treatment methods and the telltale signs they leave behind. This…

  • molecule model - gemological formulas
    Understanding Gemological Formulas

    Step 1: Introduction to Gemology Lesson 3 Back to syllabus The chemical composition of a mineral is a primary aspect of its definition as a species. That composition can be expressed in a chemical formula that identifies the…

  • gem definitions - opal
    What is a Gem?

    Step 1: Introduction to Gemology Lesson 2 Back to syllabus For thousands of years, terms such as rubies, sapphires, gems, and jewels have been in our vocabulary. However, some find defining a gem quite challenging. Not everyday…

  • Spinel-199585
    Uncommon Elements Make Uncommon Gemstones

    Step 1: Introduction to Gemology Lesson 5 Back to syllabus Why are some gems more common in nature than others? Gemology teaches us that crystalline gemstones need five things to develop: ingredients, temperature, pressure, time, and…

  • Ring #4
    How Well Do You Know Your Birthstone Gemology?

    You might be familiar with the romance of birthstones, but how well do you know birthstone gemology? Take our short quiz and learn about the composition, faceting, and value of birthstones. What Is My Birthstone? Throughout history and across…

  • 10x loupe - gemology tools
    Recommended Gemology Tools and Instruments

    Step 1: Introduction to Gemology Lesson 10 Back to syllabus Getting Started Gemology involves studying the physical and optical properties that make gems such unique little treasures. Gem identification involves analyzing these…

  • Lab-Gemology
    Guide to Career Options in Gemology

    So, you’re interested in gems, and wish to make working with gemstones your career? Fortunately, there are plentiful job opportunities in the world of gemstones, and becoming a certified gemologist is a rewarding, satisfying way to spend each day….

  • Gem Storage Case
    Guide To Organizing Your Gemstone Collection

    Your gemstone collection deserves to be organized and secure. You’ll not only find the pieces you’re looking for faster but also protect them from damage. That pile of precious stones may look opulent, but remember that gems have different…

  • rubies
    Distinguishing between Rubies and Pink Sapphires

    Rubies versus Pink Sapphires. Both are varieties of corundum. Learn the true scientific difference between the two.

  • gemstone density - cerussite
    Basics of Gemstone Density and Specific Gravity

    Gemologists sometimes measure gemstone density or specific gravity to help with gem identification. Learn the basics of this property and how to test it.

  • Emerald Hollow
    Top Spots For Gem Hunting In The US

    When you think of mining for the “big four” gemstones – diamond, ruby, sapphire, and emerald – it’s easy to imagine places like India, South Africa, and Colombia. However, there are plenty of gem hunting spots in the United States where you…

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    Build Your Own Gemology Tools

    One of the first problems student gemologists encounter is one advanced gemologists also face: high equipment costs. The variety and prices of modern gemology tools make them almost cost prohibitive for a hobbyist or someone not willing to make the…

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    Gemstone Care Guide

    Consult our gemstone care guide to learn the best cleaning methods for many popular gems. Most will respond well to warm water, mild detergent, and a soft brush at home. However, some gems do have sensitivities you should be aware of, particularly…

  • “Rosaline Pearls Necklace” by Mercury Jane is licensed under CC By 2.0
    Care Guide For Pearls And Opals

    Pearl and opal have been valued as gems throughout history and across many cultures. However, these beautiful objects have chemical compositions a bit different than most gems and require special attention before, during, and after cleaning. Our…

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    A World of Crystals

    We live in a world of crystals. The rocks that make up the planets in our solar system, including our own, are made of minerals. These minerals are composed of various elements and normally occur naturally in crystal form. Sometimes the rocks…

  • zi1632
    What is Gemstone Birefringence?

    Gems that polarize light and split it into two (or three) different directions are said to be doubly refractive. Birefringence is a measure of a gem’s double refraction and it’s one of the principal ways gemologists can identify…

  • California turquoise - Mojave Desert
    Desert Prospecting: Discovering California Turquoise

    IGS member Richard Edley shares his experiences discovering California turquoise and offers advice on desert prospecting.

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    What Is Gemstone Luster, Polish Luster, and Fracture Luster?

    Adamantine. Silky. Greasy?  These are a few of the evocative terms that can be used to describe gemstone luster. Gemstone luster simply means how a gemstone looks when it reflects light. For example, the brilliant mirror-like appearance of a…

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    What is a Crystal?

    What comes to mind when you think of crystal? Many people might visualize a beautiful, mineral object with smooth faces in regular geometric patterns. Others might imagine elegant glassware. For gemologists, there is a scientific…

  • LightoftheDesert
    What is Gemstone Dispersion?

    Have you ever seen the colors of the rainbow coming from deep within a finely cut gem? That effect is known as gemstone dispersion, or a gemstone’s “fire.” Although diamonds are well known for their dispersion, other gems can exceed their…

  • Gemstone Inclusions - Apatite in Spinel
    An Introduction To Gemstone Inclusions

    Magnification opens the door to a fascinating dimension in gemology: the inner world of gemstone inclusions.  You’ll see marvels that can rival the beauty and intrigue of the gem itself. On a practical level, identifying inclusions may help…

  • Àíäðàäèò
    What Creates Gemstone Color?

    Gemstone color owes a little to pigments and a lot to light. Some gems get their color the same way paints receive their color.  For example, if you wanted some blue paint for your bedroom, the store clerk would take white paint and add a few drops…

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    What Are Gemstone Absorption Spectra?

    Color is an obvious quality of a gem but alone it tells little about a gem. By using a spectroscope to reveal gemstone absorption spectra, a gemologist can take a fuller view of how gems interact with light and get their color. Determining which…

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    What Is Gemstone Transparency?

    Like colors, gemstone transparency – whether a gem is opaque, translucent, or transparent – is a result of light interacting with the gem. Although gemstone transparency is not a precise basis for identifying gem species, the presence and…

  • 474714937_a028691b2e_o
    What Are Lab Grown Sapphires?

    Could you tell the difference between natural sapphires and lab grown sapphires? Sapphires have been highly prized for ages. Their beauty and hardness make them ideal choices for jewelry. The demand for sapphires, however, has long exceeded…

  • Cleaning Gemstone Jewelry
    How To Clean Your Gemstone Jewelry

    What do you need to clean your gemstone jewelry? For many pieces, mild detergent, warm water, and a soft brush are a good start. However, before you decide to clean your collection yourself, or even if you leave it to a professional jeweler, add a…

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    Mechanical Gemstone Cleaning

    The principal advantage of mechanical gemstone cleaning is getting beautiful results on difficult to clean set gems with minimal effort. Although there are home kits for cleaning jewelry with ultrasonic, steam, and boiling systems, these techniques…

  • Rubies are ideal gemstones for calibrating the scale of a spectroscope.  Learn why in our basic spectroscope instructions.  “Corundum (Var. Ruby)” by Robert Lavinsky is licensed under CC By-SA 3.0
    Spectroscope Instructions

    Although based on sophisticated science, the spectroscope itself is a simple device that needs only a few adjustments to use. All models have ways of adjusting the focus and the amount of light entering the instrument. Advanced models also have ways…

  • “Discovered in 1989, this is one of the largest (2765 carats) and finest quality boulder opals ever mined.  This opal is unique not only for its size but also for its quality -- every color of the spectrum is visible which is extremely rare, even in the finest of opals.”  “Opal, Opalville Mine, Queensland, Australia” by Wikipedia Loves Art participant “Assignment_Houston_One” is licensed under CC By-SA 2.5
    Australian Opals

    Although opal can be been found all around the world, there are only a few major sources of this precious stone. Australian opals account for 95% of the world’s supply. Unique geological formations in Australia have favored the formation of this…

  • “Faceted Diamond 1” by James St. John is licensed under CC By 2.0
    What Is A Reflectometer?

    Question In my quest for a refractometer, someone suggested that I purchase a reflectometer as a more affordable alternative. However, I’m having difficulty getting much information on this tool as it relates to gemstones. Do you know anything…

  • “Opal Necklace” by James Petts is licensed under CC By-SA 2.0
    Opal Jewelry Tips

    Question I was a bit disappointed with your description of opal wearability as “Poor.” Bit harsh I think. If it’s worn as a ring I could understand the comment, but how about brooches and pendants? Not too much abrasive action on stones in…

  • “Rhodolite Garnet.” Rob Lavinsky, www.iRocks.com. Used with permission.
    What Is A Rhodolite Gem?

    Question I recently bought a rhodolite. It’s clean and has a beautiful dark red color. My problem is simply that I’m wondering if it’s truly rhodolite or some other type of garnet. This is the first time I’ve purchased this garnet…

  • “Chrysoprase inlay rings in sterling and 14k gold. Carved, cast, and inlay all done in-house by Mark Anderson” by Jessa and Mark Anderson is licensed under CC By 2.0
    Does Chrysoprase Jewelry Fade?

    Question From different sources, I’ve heard that chrysoprase fades in sunlight or heat. How sensitive is it? Does normal daytime wear affect the stone color? Should chrysoprase be worn mostly at night to preserve its vivid color? Can the color…

  • “Sphalerite Cut” by Eurico Zimbres is licensed under CC By-SA 3.0
    Sphalerite Appraisal

    Question I’ve come across what I believe is an unusual specimen and I’m looking for someone to help me come up with an approximate value for this. I’ve got a brilliant cut sphalerite that is 11.5 ct and 13mm across. It’s a brilliant…

  • “3.03ct Oval Ruby,” Winza, Tanzania, purplish red. ©All That Glitters. Used with permission.
    Ruby Buying Guide

    Ruby is one of the most sought after (and expensive) gemstones on the market. This gem’s exceptional hardness makes it very resistant to scratching. This quality makes it possible to wear ruby jewelry every day for any occasion. The…

  • A “Ceylon Blue” sapphire from Montana. This gemstone listing makes a clear distinction between the color name and the origin of the stone.  “Sapphire,” 1.04 cts., fancy round brilliant cut. © Dan Stairs Custom Gemstones. Used with permission.
    Sapphire Buying Guide

    Mention sapphire and most people will probably imagine blue colored gems. Although blue sapphires are probably the most famous examples, these exquisite corundum gemstones come in virtually every color. Except red. (Red corundum is ruby). Long…

  • “Emerald-Cut Rare Yellow Topaz from Ouro Preto, Brazil” by Wiener Edelstein Zentrum is licensed under CC By-SA 3.0
    Topaz Buying Guide

    Historically, topaz is one of the most important gemstones. Topaz’s high refractive index, hardness of 8, and capacity for taking a fabulous polish make it an excellent choice for any jewelry application. Its wide range of colors makes it easy…

  • “Serpentine Fire Opal Pendant,” Mexican fire opals and sterling silver, by Jessa and Mark Anderson is licensed under CC By 2.0
    Opal Buying Guide

    Step 4: Gem Grading Lesson 18 Back to syllabus Opal gemstones are evaluated a little differently than other gemstones. The International Gem Society opal price guide features a grading system and terms unique to opals. A full…

  • 3.60-ct spinel - spinel buying guide
    Spinel Buying Guide

    Natural spinel has long been overlooked. Superstars of the gem world with a similar appearance, like ruby and sapphire, as well as commonplace synthetic versions have taken its spotlight, so to speak. Now, spinel has become a popular gemstone…

  • Constellation - Oregon sunstone buying
    Oregon Sunstone Buying Guide

    Buying and selling Oregon sunstone can be difficult. The beauty and diversity of this gem make it hard for people to describe and price accurately. In my research, I’ve looked for commonalities and averages in order to best describe and price…

  • Sample Gemology Questions - Brilliant Cut
    IGS Certification Exam: Sample Gemology Questions

    The first step students will face in the International Gem Society (IGS) certification process is passing three 100-question written tests. All the questions are based on the materials in the IGS Learning Center. What’s The Test Like? The…

  • story gemstone - rhodolite garnet
    Precision Faceting A Story Gemstone: Choosing Rough

    Introduction Every distinctive, precision faceted gemstone I cut has a wonderful, personal tale to tell. My customers come to my lapidary studio with dreams. As a precision faceter, I’m committed to making their desires and visions converge…

  • gem design - sunshine stone detail
    Precision Faceting A Story Gemstone: Gem Design

    Introduction Once you’ve selected your rough stone, the next step to creating your one-of-a-kind story gemstone is choosing the gem design. At this stage, the jeweler usually enters the process. Your precision faceter can recommend professional…

  • faceting equipment - cutting concave facets
    Precision Faceting A Story Gemstone: Faceting Equipment

    Introduction Compared to gems cut twenty years ago, faceted gems today are amazing pieces of craft and art. Modern faceting equipment makes a difference. In this article, I’ll introduce prospective clients to tools such as precision faceting…

  • faceting process - dopping station
    Precision Faceting A Story Gemstone: The Faceting Process

    Introduction Precision faceting one gemstone at a time takes both patience and dedication. Custom lapidaries want to excel at their craft. For us, making each and every gem is a work of art. After investing time and money in gem rough, design,…

  • custom faceting - detail
    Precision Faceting a Story Gemstone: Custom Faceting Advice

    Introduction In this article, I’ll introduce one more story and finally unveil pictures and photos of the six finished story gems from this precision faceting series. I’ll also share some tips for consumers considering custom faceting for their…

  • gemstone pendulum - bronze rutile quartz pendant
    Faceting a Gemstone Pendulum to Feature Inclusions

    Showcase the amazing inclusions in minerals like rutilated quartz in a gemstone pendulum design. Learn how to facet these gems into stunning jewelry pieces.

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