What Is The Difference Between Gemology And Mineralogy?

An Overview of the Principal Differences Between Gemology and Mineralogy

• Gemologists and mineralogists both study minerals. However, gemology focuses on a subset of minerals used as gemstones in addition to non-mineral gemstones (like amber and pearls) and synthetic materials. Mineralogy focuses on minerals of all kinds (and only minerals).
• Gemological analysis is limited to testing samples with non-destructive procedures. In contrast, mineralogical analysis can include a broader range of tests, even some that destroy portions of the test samples.
• Gemology primarily contributes to the gem and jewelry trade, both the industry and their consumers. Mineralogy has applications within many industries, from agriculture to aerospace.

What Do Gemologists and Mineralogists Study?

Gemologists and mineralogists both study minerals. Prized gemstones such as natural diamonds, rubies, sapphires, and emeralds are all minerals. Diamonds are a unique mineral species. Rubies and sapphires are varieties of the corundum mineral species. Emeralds are a variety of the beryl mineral species. Gemologists focus on minerals celebrated for their appearance and often cut for display or jewelry use. Mineralogists focus on minerals of all types and with many applications.

If this is the case, why aren't gemology and mineralogy considered one discipline, with gemology focused on a subset of minerals?

What is the Difference Between Gemstones and Minerals?

In terms of subject matter, gemology does indeed cover a subset of minerals, but it also covers non-mineral materials. Gemologists study gemstones. However, the definition of "gemstone" is more subjective than that of "mineral." A mineral is a naturally occurring solid substance with a definite chemical composition and a specific crystal structure. On the other hand, gemstones are minerals and non-minerals selected for their beauty and durability and cut for ornamentation, including jewelry use.

Most gemstones — like the aforementioned diamonds, rubies, sapphires, and emeralds — are minerals, but there are three notable non-mineral types of gemstones.

Non-Crystalline Gems

A well-known and highly valued example of a non-mineral gemstone is a pearl. Although pearls may be solid substances, they lack a crystal structure. Materials without crystal structure are considered amorphous and, thus, are not minerals.

Pearls are actually created by mollusks through biological processes. Other examples of organic, non-crystalline gemstones include amber, coral, ivory, jet, and shell.

Non-crystalline gems can also form through inorganic processes within the Earth. Obsidian and opal are notable examples.

Synthetic and Treated Gems

Humans have made gems from artisanal glass for millennia. Scientists have also created gems in laboratories with physical and optical properties identical to minerals like diamonds, rubies, sapphires, emeralds, etc. However, these synthetic or lab-created gemstones, by definition, aren't minerals because they don't occur naturally. For example, synthetic diamonds are real diamonds with properties identical to mined diamonds, but they're not minerals.

In recent years, the quality and quantity of synthetic gems available to consumers has grown tremendously. Detecting synthetic gems has become an essential area of research for gemologists.

Many gemstones, both natural and synthetic, also receive treatments or enhancements to improve their color, optical performance, and stability.

Homocreates

Homocreates are lab-created materials that have no known natural equivalent. Therefore, by definition, these are not minerals. Most such materials have primarily industrial uses, but some have found their way into the gem world, such as strontium titanate, gadolinium gallium garnet (GGG), and yttrium aluminum garnet (YAG).

Perhaps the most well-known homocreate in the jewelry world, cubic zirconia (ZrO₂) or CZ, was long thought to have no natural equivalent. However, a 2017 study by Nicholas E. Timms et al. documented geological evidence that the meteorite impact that created the Mistastin Lake crater in Canada during the Hadean eon (4.5-4 billion years ago) also formed microscopic grains of cubic zirconia. For this to have occurred, the impact generated a temperature of over 2,370° C, the hottest recorded on the Earth's surface. (2017) Any cubic zirconia formed from this unique and extreme geological event would undoubtedly qualify as a mineral. However, the cubic zirconia used in jewelry wasn't formed this way.

Not All Minerals Are Gemstones

While most gemstones are minerals, not all minerals are gemstones. As of November 2024, the International Mineralogical Association (IMA) officially recognizes 6,100 valid mineral species. Only around 3,000 have been cut, polished, and admired for their appearance. Most of these have only rarely been cut as curiosities. Only around 300 minerals have ever been used in jewelry, and only around 100 regularly appear in jewelry. The vast majority of minerals can't function as gemstones. Many minerals are too soft to be faceted and polished or too fragile for wear. Some occur only in microscopic sizes. Some occur so rarely that no economic demand for them exists.

How Do Gemological and Mineralogical Analytical Methods Differ?

Historically, gemology and mineralogy have shared many tools and tests for material investigation. However, a critical issue significantly restricts the tests gemologists typically conduct when studying gemstones. Gemstones (minerals or not) usually hold high value. This value may have economic, historical, or personal dimensions. As a result, gemologists usually use non-destructive and non-invasive methods exclusively. The analytic process, from identifying the gem material to detecting synthetic origins and treatments, must not destroy or harm the gem.

Classic Gemology Testing Methods

Gemologists typically utilize the following classic, non-destructive tools and tests also used in classic mineralogy:

• Refractometer
• Polariscope
• Dichroscope
• Microscope and loupe
• Spectroscope
• Specific gravity testing
• Ultraviolet testing

Gemologists rarely use classic destructive tests, such as acid, hot point, and scratch testing. These may be used as a last resort. However, gemologists never use these tests on finished gems but may use them on rough material.

Advanced Testing Methods in Mineralogy

While classic tests continue to help gemologists with identification, ever-evolving gem use, treatments, and synthetic materials pose new challenges. As a result, modern gemology also utilizes some of the advanced testing methods used in mineralogy.

These methods may include:

• Electron Probe Microanalysis (EPMA): a procedure for determining the chemical composition of microscopic-size samples.
• X-Ray Fluorescence Spectrometry (XRF): a procedure for determining chemical composition.
• Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS): a precise, state-of-the-art method for identifying chemical composition.
• X-ray diffraction (XRD): a procedure for determining a mineral's crystal structure. It can differentiate between polymorphic mineral species (which have the same chemical composition but different crystal structures, such as aragonite and calcite).
• Transmission Electron Microscopy (TEM): a procedure that makes it possible to see the structure and composition of minerals at the atomic scale. This method can help identify possible mineral nano-inclusions.
• Raman spectroscopy: a spectroscopic method that utilizes a laser for mineral identification.
• Fourier Transform Infra-Red (FTIR) spectroscopy: a spectroscopic method primarily used to identify water-bearing minerals and organic materials.
• Ultraviolet-visible-Near Infra-Red (UV-vis-NIR) spectroscopy: a procedure for identifying elements or ions that cause color in minerals as well as some color treatments in gemstones.

Which Advanced Mineralogy Tests are Non-Destructive?

Each advanced testing method has a specific sample preparation process. These may involve cutting a sample from the test mineral, polishing a flat surface, or grinding the sample into powder. (Some methods have multiple preparation processes). Of course, gemologists try to avoid tests that destroy or damage their test samples. Therefore, the advanced spectroscopic methods are the most useful for gemology. These don't require any destructive sample preparation.

Raman Spectroscopy

One of the principal modern gemological testing methods, Raman spectroscopy doesn't require any sample preparation for crystals and gemstones. It's a quick and reliable test and can also be used on mounted gems, a boon for gemologists.

Fourier Transform Infra-Red (FTIR) Spectroscopy

Scientists can conduct this test in several ways. Attenuated total reflectance (ATR) requires one polished surface on a specimen for quick identification. This test can help gemologists detect treatments in emerald, jade, and turquoise, as well as synthetic gemstone origins, in a non-destructive manner. Transmission (TR mode) is a more precise FTIR spectroscopy technique that requires a powdered sample mixed with potassium bromide (KBr). However, gemologists won't use TR mode because they would have to damage and possibly destroy the gemstone to get a powdered sample.

X-Ray Fluorescence Spectrometry (XRF)

Scientists can utilize XRF spectrometry in destructive and non-destructive techniques. They can analyze homogenized samples (ground into powder) for a more precise test or analyze samples without any preparation. Gemologists use the non-destructive technique.

Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)

LA-ICP-MS helps identify a sample's chemical composition and trace elements. Trace element composition can also help indicate a gemstone's geographic origin. However, LA-ICP-MS is a slightly destructive testing method. The test requires just a few milligrams or less of material from the sample. Some faceted gemstones can have the material removed from the girdle or other areas hidden by the mounting. A tiny amount of material removed from these places won't impact the gem's appearance or optical performance. Nevertheless, LA-ICP-MS may not be appropriate for testing historic or high-value gemstones.

Working with Gemstones in Jewelry Settings

Unlike mineralogy, gemology often involves analyzing materials mounted into jewelry pieces. Gemologists often can't remove the gem from its setting without damaging either or both. Sometimes, the owners may simply not allow it. Raman spectroscopy can handle these cases. It can even help gemologists deal with further restrictions. Some gemstones in museums or private collections can't be sent to a laboratory. Gemologists can use portable Raman spectrometers for in situ analysis.

What are the Applications of Mineralogy and Gemology?

Mineralogists study minerals in general. Specifically, they study the formation and alteration of minerals. Some mineralogists investigate the use of minerals in industries such as agriculture, construction, and energy. Other mineralogists focus on crystal structures and the arrangement of isomorphic elements within crystal lattices. Mineralogists aren't only focused on the Earth. Some mineralogists study minerals and rocks from the Moon and Mars. For example, based on data obtained from Mars probes, mineralogists try to predict the mineral composition of the planet's surface and its possible conversion into soil.

Gemologists focus specifically on the study of gemstones, minerals or not. They focus on not only identifying gems but also detecting treatments and determining their origins. Gemologists also evaluate gemstone quality and value and devise standards for those evaluations. Of course, gemology makes its most significant impact on the gemstone and jewelry industries. Since gems and jewelry often have historical, cultural, and artistic significance, gemology can also contribute to history, cultural studies, and art.

What Other Disciplines Should Mineralogists and Gemologists Know?

Mineralogy has connections with crystallography, geology, petrology, paleontology, chemistry, physics, and biology. Learning any of these disciplines would benefit mineralogists. For example, mineralogists often study regional geology and petrology to fully understand a mineral's origin and formation. When the cause of a mineral's color is unknown, mineralogists will dive into crystallography and the physics of spectroscopy. 

Gemology has a close connection to mineralogy. It also intersects with the fields of archeology, art history, cultural history, material sciences, marketing, and economics. Gemologists could benefit from learning more about any of these fields.

How Can Learning Mineralogy Benefit Gemologists?

Despite differences in subject matter, methods, and applications, mineralogy and gemology have much in common. Most gems are minerals, and gemology's principal identification tools and methods come from mineralogy. However, gemology courses usually don't include deep learning about mineralogy. As a result, gemologists often need help connecting their gemstone observations to nature — in this case, mineralogical and geological processes.

Mineralogy can help gemologists identify the source of a natural rough gem or crystal — and whether a suspected location is even geologically capable of producing the sample in question. Mineralogy can also help gemologists develop marketing plans for a gemstone informed by those geological processes. For example, let's consider alexandrite gemstones.

"Emerald by day, ruby by night" is a romantic description of alexandrite's color change effect. Green in sunlight but red in incandescent light is alexandrite's most prized color change, but other color changes do occur. This oval-cut alexandrite from Zimbabwe changes from a blueish green in sunlight to a silvery pink in indoor lighting. 0.30 cts, 5.06 mm x 3.17 mm. Video © Rob Lavinsky, mineralauctions.com. Used with permission.

Why is Alexandrite So Rare? A Mineralogical Explanation

Alexandrite is a well-known and highly valued gemstone, and good quality material is extremely rare. But what makes alexandrite so rare? Rarity can mean different things in the gem world, and material scarcity doesn't automatically make a gem valuable or desirable.

Alexandrite is a chromium-bearing variety of chrysoberyl. Chemically, chrysoberyl is beryllium aluminum oxide (BeAl₂O₄). The trace amounts of chromium (Cr) in alexandrite create its coveted color-change effect. A chromium admixture to beryllium aluminum oxide is necessary for the formation of alexandrite. As the gemologist Edward Gübelin notes:

Alexandrite owes its great rarity to the fact that the geochemical conditions are highly accidental because beryllium and chromium do not typically occur within the same rock suites. Beryllium is concentrated in the pegmatitic and pneumatolytic phases which themselves are devoid of chromium. The latter, on the other hand, is more frequently present in mafic rocks. Therefore the formation of alexandrite may only be expected in places where the ingredients of these rocks can meet[.] (204)

These geochemical circumstances are exceptional (almost a miracle) in nature.

Gemology can address the optical performance of an alexandrite gemstone, assess its quality, and discuss the romantic history and lore behind this celebrated gemstone. All these elements can help promote this gem to potential consumers. Mineralogy can add another dimension to this sales pitch. A knowledgeable gemologist could explain the "natural miracle" that an alexandrite embodies.

Gemology and Mineralogy United

Gemologists and mineralogists work on slightly different materials, use different analytical methods, and focus on different goals. Nevertheless, knowledge of mineralogy can benefit gemologists (and knowledge of gemology can benefit mineralogists). Those with expertise in multiple disciplines can find new, useful, and fascinating things along their borders.

Works Cited

Gübelin, Edward. "Alexandrite From Lake Manyara, Tanzania." Gems & Gemology, Fall 1976. (Accessed 2/17/24)

Timms, Nicholas E., et al. "Cubic zirconia in >2370 °C impact melt records Earth's hottest crust." Earth and Planetary Science Letters, Volume 477, 1 November 2017, Pages 52-58. (Accessed 2/17/24)

Olena Rybnikova, PhD

Olena Rybnikova is a gemologist and mineralogist. She has a PhD in mineralogy and petrology specializing in beryllium minerals and is a certified Applied Jewelry Professional accredited by the Gemological Institute of America. Her passion is actively promoting knowledge and appreciation of nature, geology, and gemstones.

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