Types of Gemstones

by Karat Designs on Jul 30 2025

Since ancient times, humans have been drawn to shiny, colorful stones, shells, and crystals. These natural treasures were often seen as symbols of status and power. Across many cultures, gemstones have also been associated with peace, prosperity, and happiness.

A few centuries ago, gemstones began to be grouped into “precious” and “semi-precious” categories. While this classification is still commonly used, it is not always consistent. For instance, diamonds are considered precious stones, yet some may sell for relatively low prices per carat. Meanwhile, certain garnets—classified as semi-precious—can be quite expensive. Because of this inconsistency, many jewelers prefer the term “colored stones” for gems other than diamonds.

Precious Stones

Precious gemstones are valued for their rarity, durability, and beauty. They are generally more expensive than semi-precious stones. The four traditionally recognized precious stones are diamond, emerald, ruby, and sapphire.

Diamond

Color: Colorless (also found in yellow, brown, blue, pink, and other rare colors)
Hardness (Mohs scale): 10
Mineral group: Carbon
Sources: South Africa, Botswana, Russia, Canada, Australia, India, Angola, Namibia

The word “diamond” comes from the Greek word adamas, meaning “unbreakable” or “invincible,” reflecting its exceptional hardness and durability. Formed deep within the Earth under intense heat and pressure, diamonds are the hardest naturally occurring substance known, making them highly valued in both jewelry and industrial use.

Diamonds are prized for their brilliance, fire, and ability to reflect light in a way few other gemstones can match. While most are colorless, they can also occur in rare and highly valuable fancy colors such as pink, blue, yellow, and green, with intense, evenly distributed color being the most desirable.

Many diamonds contain tiny natural imperfections known as inclusions. These are common and help gemologists identify whether a stone is natural or synthetic. Completely flawless diamonds are extremely rare and command very high prices. Despite their hardness, diamonds can still chip or fracture if struck at the right angle, so they still require careful handling.

Emerald

Color: Deep green to dark green
Hardness (Mohs scale): 7.5–8
Mineral group: Beryl
Sources: Colombia, Brazil, Zimbabwe, South Africa, Afghanistan, USA

The word “emerald” comes from the Greek smaragdos, meaning “green stone.” Its rich green color, combined with rarity and durability, makes it highly prized. Deep, vivid green stones are the most desirable.

Emeralds often contain natural inclusions, which are considered part of their character. Completely flawless emeralds are extremely rare and can be more valuable than diamonds. Although fairly hard, emeralds can crack if struck or exposed to sudden temperature changes. Treated stones should not be cleaned with ultrasonic devices, as this can remove protective oils and reveal internal flaws.

Ruby

Color: Red shades ranging from pinkish to deep crimson
Hardness (Mohs scale): 9
Mineral group: Corundum
Sources: Myanmar, Thailand, Sri Lanka, Tanzania

Ruby is the red variety of corundum, the same mineral family as sapphire. Only red corundum is classified as ruby; all other colors are considered sapphires.

The name comes from the Latin word ruber, meaning “red,” while in Sanskrit it is called ratnaraj, or “king of gemstones.” The most valuable rubies display a vivid “pigeon’s blood” red color.

Rubies are admired for their intense color, durability, and rarity. Although very hard, they can still chip if handled roughly.

Sapphire

Color: Blue, pink, yellow, green, white, orange, purple, and more
Hardness (Mohs scale): 9
Mineral group: Corundum
Sources: Sri Lanka, Burma, Thailand, Australia, India, Brazil, Africa

Sapphire is also part of the corundum family, with all colors except red classified under this name. While blue is the most recognized shade, sapphires actually occur in many colors, often called “fancy sapphires” when not blue.

The value of sapphire depends on color, clarity, and size. High-quality stones are rare and require skilled cutting to maximize their appearance. Synthetic versions are also widely produced, closely resembling natural stones in composition and appearance.

Sapphires are highly durable and suitable for everyday wear, though they can still chip under strong impact.

Semi-Precious Stones

Semi-precious gemstones include all other stones valued for beauty but not classified as diamond, ruby, sapphire, or emerald. These stones vary widely in price and availability.

Alexandrite

Color: Green in daylight, red under artificial light
Hardness: 8.5
Mineral group: Chrysoberyl
Sources: Russia, Sri Lanka, Brazil, Madagascar

Alexandrite is a rare gemstone known for its dramatic color change depending on lighting. It was first discovered in Russia in the 19th century and named after Tsar Alexander II.

Fine-quality alexandrite is extremely rare and highly valuable, sometimes even more than traditional precious stones.

Amethyst

Color: Purple shades
Hardness: 7
Mineral group: Quartz
Sources: Brazil, Uruguay, India, Russia, Africa

Amethyst is a purple variety of quartz colored by trace elements. Deep purple stones are the most valuable. The name comes from the Greek word meaning “not intoxicated,” as it was historically believed to prevent drunkenness.

It is also considered a symbol of peace and good fortune.

Aquamarine

Color: Light blue to sea blue
Hardness: 7.5–8
Mineral group: Beryl
Sources: Brazil, Pakistan, Madagascar, Nigeria, USA

Aquamarine is a blue-green variety of beryl, named after the Latin words for “water” and “sea.” It is admired for its calming ocean-like colors.

The deeper the blue, the more valuable the stone is considered. Its durability makes it popular in jewelry.

Citrine

Color: Yellow to orange-brown
Hardness: 7
Mineral group: Quartz
Sources: Brazil, Madagascar, Russia, Spain

Citrine is a yellow variety of quartz often mistaken for topaz. Its name comes from the French word for “lemon.”

It is a durable gemstone, making it suitable for everyday wear, and is appreciated for its warm golden tones.

Garnet

Color: Red, green, yellow, brown, black
Hardness: 6.5–7.5
Sources: India, Sri Lanka, USA, Africa, Australia

Garnet is a group of minerals found in many colors. Its name is inspired by its resemblance to pomegranate seeds.

Different varieties include pyrope, almandine, and rhodolite, each with unique color characteristics. Some garnets are highly valued for their rich, vibrant tones.

Iolite

Color: Blue-violet to grayish blue
Hardness: 7–7.5
Mineral group: Cordierite
Sources: India, Sri Lanka, Brazil, Africa

Iolite is known for its violet-blue color and was historically used by Viking navigators to help locate the sun.

It is sometimes confused with tanzanite but tends to be darker in tone.

Onyx

Color: Black, white, or banded
Hardness: 6.5–7
Mineral group: Chalcedony (Quartz family)
Sources: India, Brazil, USA, Madagascar

Onyx is a banded variety of chalcedony often dyed black for jewelry use. It has been used since ancient times for carvings and decorative pieces.

Opal

Color: Multiple colors with iridescence
Hardness: 5–6.5
Sources: Australia, USA, Mexico, Brazil

Opal is famous for its play of color, known as opalescence, where light creates shifting rainbow-like effects within the stone.

It contains water and must be protected from heat and dryness to prevent cracking.

Pearl

Color: White, cream, pink, black, and more
Hardness: 2.5–4.5
Sources: Oceans of Japan, China, Australia, Persian Gulf

Pearls are organic gemstones formed inside mollusks when layers of nacre build up around an irritant.

They may be natural or cultured, with perfectly round pearls being the rarest and most valuable.

Peridot

Color: Yellow-green to olive green
Hardness: 6.5–7
Mineral group: Olivine
Sources: USA, Pakistan, Myanmar, China, Africa

Peridot is one of the few gemstones that appears in only one color family. Its green hue comes from its natural iron content.

It forms deep within the Earth under extreme heat and pressure.

Tanzanite

Color: Blue, violet-blue, purple
Hardness: 6–7
Sources: Tanzania only

Tanzanite is a rare gemstone discovered in Tanzania in the 1960s. It is known for its striking blue-violet color and is only found in one region of the world.

It can show multiple colors depending on viewing angle and lighting.

Topaz

Color: Yellow, blue, pink, colorless, orange
Hardness: 8
Sources: Brazil, Sri Lanka, USA, Nigeria

Topaz is a durable gemstone often found in golden shades. Some varieties can change color when heated.

Despite its strength, it can still fracture if struck.

Tourmaline

Color: Wide range including black, pink, green, blue
Hardness: 7–7.5
Sources: Brazil, Africa, USA, Sri Lanka

Tourmaline is a highly diverse gemstone that appears in many colors, sometimes even multiple colors in a single stone.

Each variety has its own name, such as rubellite for red tourmaline. It is durable and widely used in jewelry.

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