Gemstone Education
Understanding natural gemstones—their properties, varieties, treatments, origins, and the qualities that make each one unique.
Every gemstone has a story written in chemistry, geology, time, and circumstance. Color, clarity, hardness, inclusions, origin, and treatment all contribute to what makes a stone distinctive.
This guide explores the characteristics of some of the gemstones you'll encounter at Elementls, along with the terminology and considerations that can help you evaluate them.
Understanding Gemstones
Gemstone value and appeal aren't determined by a single characteristic. Color, clarity, cut, size, rarity, durability, origin, treatment, and market demand can all play a role.
Some stones are prized for exceptional color. Others are valued for unusual inclusions, remarkable size, rarity, historical significance, or an origin associated with particularly desirable material. There is no single formula for what makes a gemstone extraordinary.
NATURAL, TREATED & ENHANCED
Gemstones may undergo treatments to improve their color, clarity, durability, or overall appearance. Common treatments include heating, irradiation, filling, diffusion, and fracture filling, depending on the gemstone.
Treatment isn't necessarily a negative—it is part of the history and commercial reality of many gemstones. What matters is understanding whether a stone has been treated and how that treatment may affect its appearance, durability, care requirements, and value.
When treatment information is known, Elementls identifies it in the individual product listing.
GEMSTONE GUIDE
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CHOOSING A GEMSTONE
There is no single definition of the "best" gemstone.
When evaluating a stone, consider what matters most to you: color, size, clarity, rarity, durability, origin, treatment, craftsmanship, or simply whether the stone has a character that draws you in.
For jewelry, consider durability and intended wear. For collecting, rarity, provenance, unusual characteristics, and historical significance may matter more. And sometimes the most compelling stone is simply the one you can't stop looking at.
AMETHYST
Amethyst is the purple variety of quartz, ranging from delicate lilac to deep, saturated violet. Its color is generally associated with trace amounts of iron and natural irradiation, with differences in color influenced by the geological conditions in which the crystal forms.
Amethyst is relatively durable, with a Mohs hardness of 7, making it suitable for most types of jewelry and a popular choice for collectors. Particularly prized material can display strong, even color and exceptional clarity, while natural inclusions and unusual formations can add character to individual specimens.
Major sources: Brazil, Uruguay, Zambia, Bolivia, and other locations
Mohs hardness: 7
Typical color: Lilac to purple
Common treatment: Heat treatment may alter or remove the purple color and can produce citrine
AQUAMARINE
Aquamarine is the blue to blue-green variety of beryl, the same mineral family that includes emerald. Its name comes from the Latin words for “water of the sea,” a fitting reference to its range of cool blue and blue-green hues.
Aquamarine is prized for its clarity and often occurs as transparent crystals with relatively few visible inclusions. Color can range from very pale blue to a more saturated blue-green, with deeper blue material generally considered more desirable. Aquamarine has a Mohs hardness of 7.5–8, making it well suited to jewelry.
Major sources: Brazil, Pakistan, Madagascar, Nigeria, Mozambique, and other locations
Mohs hardness: 7.5–8
Typical color: Pale blue to blue-green
Common treatment: Heat treatment is commonly used to reduce green tones and produce a bluer appearance
CITRINE
Citrine is the yellow to orange variety of quartz, ranging from pale lemon and golden yellow to deeper honey and orange tones. Natural citrine is relatively uncommon, which makes naturally occurring color especially interesting to collectors.
Much of the citrine available commercially is produced by heat-treating amethyst or amethyst-containing quartz. Heat treatment can produce colors ranging from yellow to orange, and treated material can be beautiful in its own right. When the distinction is known, the difference between natural and heat-treated citrine is important information when evaluating a stone.
Citrine has a Mohs hardness of 7, making it durable enough for most jewelry applications.
Major sources: Brazil, Bolivia, Madagascar, Zambia, and other locations
Mohs hardness: 7
Typical color: Yellow, golden, orange, and honey tones
Common treatment: Heat treatment; much commercial citrine is heat-treated amethyst
EMERALD
Emerald is the green variety of beryl and one of the world's most historically celebrated gemstones. Its color ranges from yellowish green to deep bluish green, with vivid, saturated green generally considered the most desirable.
Unlike many transparent gemstones, emeralds commonly contain visible inclusions. These inclusions are often referred to by the French term jardin, meaning “garden,” and can be an important part of the stone's identity. Exceptional emeralds combine desirable color with transparency, but clarity expectations for emerald are different from those for many other gemstones.
Emerald has a Mohs hardness of 7.5–8, although its natural inclusions and internal fractures can make it more vulnerable to damage than its hardness alone suggests.
Major sources: Colombia, Zambia, Brazil, Ethiopia, and other locations
Mohs hardness: 7.5–8
Typical color: Green to bluish green
Common treatment: Clarity enhancement with oils or resins is common
GARNET
Garnet is a group of closely related minerals rather than a single gemstone, occurring in a remarkably broad range of colors. Although red is the most familiar, garnets can also be green, orange, pink, yellow, brown, and even nearly black. Different garnet species and compositions produce this extraordinary variety.
Some of the most sought-after garnets include vivid green tsavorite, orange spessartine, rich red rhodolite, and the exceptionally rare blue garnet. Garnets can also occur as mixtures of different species, creating colors and characteristics that don't fit neatly into a single category.
Garnets generally have a Mohs hardness of 6.5–7.5, depending on species and composition. Most are durable enough for jewelry, although individual varieties can differ in their resistance to scratching and impact.
Major sources: Tanzania, Kenya, Mozambique, Madagascar, Sri Lanka, India, Brazil, and other locations
Mohs hardness: 6.5–7.5
Typical colors: Red, green, orange, pink, yellow, brown, and more
Common treatment: Most garnets are not routinely treated, although individual material may receive treatment
RUBY
Ruby is the red variety of corundum, the same mineral species that produces sapphire. Its color ranges from pinkish red to vivid red, with the most prized material displaying strong, saturated color. The finest rubies can command extraordinary prices because exceptional color, clarity, size, and origin are all relatively rare.
Trace amounts of chromium are responsible for ruby's characteristic red color and can also produce fluorescence under ultraviolet light. Natural rubies commonly contain inclusions, and their presence can help distinguish natural material from synthetic stones and contribute to a stone's individual character.
Ruby has a Mohs hardness of 9, second only to diamond among commonly encountered natural gemstones, making it exceptionally well suited to jewelry.
Major sources: Myanmar, Mozambique, Sri Lanka, Madagascar, Vietnam, Thailand, and other locations
Mohs hardness: 9
Typical color: Pinkish red to vivid red
Common treatments: Heat treatment is widespread; fracture filling and other treatments may also occur
SAPPHIRE
Sapphire is the gem variety of corundum in every color except red, which is classified as ruby. Although blue is the color most strongly associated with sapphire, the species can occur in yellow, pink, green, orange, purple, and other colors.
Blue sapphire ranges from pale blue to deep, saturated blue, with color influenced by trace elements including iron and titanium. Some sapphires display asterism—a star-like optical effect caused by aligned inclusions—and are cut as cabochons to emphasize the phenomenon.
Sapphire has a Mohs hardness of 9, making it exceptionally durable and well suited to everyday jewelry. Natural inclusions are common and can provide useful information about a stone's origin and treatment history.
Major sources: Sri Lanka, Madagascar, Myanmar, Kashmir, Australia, Tanzania, and other locations
Mohs hardness: 9
Typical colors: Blue, yellow, pink, orange, green, purple, and colorless
Common treatments: Heat treatment is common; diffusion and other treatments may also occur
TANZANITE
Tanzanite is the blue to blue-violet variety of the mineral zoisite and is found commercially in only one known region: the Merelani Hills near Mount Kilimanjaro in Tanzania. Its combination of vivid color, limited geographic origin, and relative scarcity has made it one of the most distinctive modern gemstones.
Tanzanite is strongly pleochroic, meaning it can display different colors when viewed from different directions. Depending on the orientation of the crystal, blue, violet, and sometimes burgundy or brownish tones may be visible. Most tanzanite is heat-treated to enhance its desirable blue and violet colors and reduce brownish tones.
With a Mohs hardness of 6–7, tanzanite is somewhat softer and more vulnerable to impact than sapphire or ruby. It is well suited to earrings, pendants, and other jewelry that receives less impact, while rings require greater care.
Source: Merelani Hills, Tanzania
Mohs hardness: 6–7
Typical color: Blue, violet-blue, and blue-violet
Common treatment: Heat treatment is standard for most gem-quality tanzanite
TOURMALINE
Tourmaline is a diverse family of minerals celebrated for its extraordinary range of colors. It can occur in green, pink, red, blue, yellow, brown, black, and multicolored combinations, sometimes within a single crystal.
Gem-quality tourmaline is most commonly associated with the elbaite variety. Trade names such as rubellite, indicolite, and watermelon tourmaline describe particularly recognizable colors or patterns. Tourmaline can also display strong pleochroism, with its apparent color changing depending on the viewing direction.
Tourmaline has a Mohs hardness of 7–7.5, making it suitable for most jewelry applications. Some exceptional material is prized for unusual color, remarkable clarity, size, or locality, while natural inclusions and distinctive growth patterns can add character to collector specimens.
Major sources: Brazil, Afghanistan, Pakistan, Mozambique, Nigeria, Madagascar, California, and other locations
Mohs hardness: 7–7.5
Typical colors: Green, pink, red, blue, yellow, black, brown, and multicolored
Common treatments: Heat treatment and irradiation may be used for certain colors or material
