OSKA · JEWELRY ATELIER
Gemstone Guide
From Earth’s depths through ancient civilizations to contemporary jewelry: explore the geological origins and human history of 18 gemstones.
Images are digital studio illustrations of gem types, not photographs of specific certified specimens.
Diamond
NATURAL DIAMOND CUTS
Digital studio renderings, not photographs of specific stones offered for sale.
- Colour
- Colourless to fancy colours
- Hardness (Mohs)
- 10
- Birth Month
- April
Its Journey From Formation To Today
The diamond’s journey began long before human history, deep in Earth’s mantle. Under exceptional pressure and heat, carbon atoms arranged themselves into an unusually strong crystal structure. Many natural diamonds formed hundreds of millions or billions of years ago. Much later, powerful volcanic eruptions carried some of them upward in kimberlite rock. Weathering and rivers released others into gravel deposits.
For centuries, people found diamonds in Indian riverbeds. The stones entered royal treasures and luxury jewelry, before major discoveries in Brazil in the eighteenth century and South Africa in the nineteenth century transformed the trade. South African finds in 1869 helped launch modern diamond mining.
Advances in cutting and grading revealed ever more brilliance. Today natural diamonds and laboratory-grown diamonds are assessed with their different origins clearly identified. A natural diamond is more than a sparkling gem: it is a surviving piece of Earth’s deep history.
Meaning
Eternal commitment, strength and purity; the classic engagement stone.
Care
Clean with warm soapy water and a soft brush; store apart from other pieces, as it scratches softer stones.
Lab-Grown Diamond
LAB-GROWN DIAMOND CUTS
Digital studio renderings, not photographs of specific stones offered for sale.
- Colour
- Colourless (D–H), fancy colours
- Hardness (Mohs)
- 10
- Birth Month
- April
Its Journey From Formation To Today
The story of laboratory-grown diamond began with scientists trying to understand a mineral that nature forms deep inside the Earth. In the 1950s, reliable high-pressure, high-temperature (HPHT) diamond growth became possible, first mainly for industrial applications.
Gem-quality laboratory diamonds followed in the 1970s. Chemical vapor deposition (CVD), developed further in subsequent decades, made it possible to build diamond crystals layer by layer from carbon-bearing gases. Controlled production could create a diamond over days or weeks rather than over geological ages.
Colorless jewelry-quality laboratory diamonds became more widely available during the 2010s. Today specialist laboratories can identify growth characteristics and distinguish origins. Both natural and laboratory-grown stones are diamond; their different journeys are part of their identity.
Meaning
Chemically, physically and optically identical to mined diamond; traceable and more accessible.
Care
Same care as natural diamond: soapy water, soft brush; ultrasonic cleaning is safe.
Emerald
- Colour
- Green to bluish green
- Hardness (Mohs)
- 7,5–8
- Birth Month
- May
Its Journey From Formation To Today
Emerald forms when the right rocks and mineral-bearing fluids meet under unusual geological conditions. Beryl gains its characteristic green when trace chromium or vanadium enters the crystal. Tiny inclusions and trapped fluids can preserve clues to the conditions in which the stone grew.
Emerald mining in the eastern desert of ancient Egypt helped give the gem an early royal reputation. Centuries later, Colombian emeralds entered global trade during the sixteenth century and became celebrated for their intense green.
Today Colombia, Zambia, Brazil and other sources supply emeralds for modern jewelry. Gemologists assess color, clarity, inclusions and any clarity-enhancement treatments. The natural features inside an emerald often tell as much of its story as the green surface does.
Meaning
Rebirth, wisdom and love; the most prized member of the beryl family.
Care
Most emeralds are oil-treated: avoid ultrasonic and steam cleaning, heat shocks and knocks; wipe with lukewarm water and a soft cloth.
Sapphire
- Colour
- Blue; also pink, yellow, white
- Hardness (Mohs)
- 9
- Birth Month
- September
Its Journey From Formation To Today
Sapphire is gem-quality corundum, an aluminum oxide mineral that can form in metamorphic and certain igneous environments. Iron and titanium often contribute to blue coloration. Uplift, erosion and rivers have moved many sapphire crystals from host rocks into ancient gravels.
Sri Lanka has supplied sapphires for centuries, sending them along trade routes to Asian and European courts. Blue sapphires gained associations with royalty and faith. A discovery in Kashmir in 1881 brought some of the most celebrated velvety blue gems into the jewelry world.
Today sapphires come from several countries and can be pink, yellow, colorless or blue. Modern gemology assesses treatments as well as color and cut. Each sapphire carries both geological and cultural history.
Meaning
Loyalty, wisdom and nobility; a corundum, very durable for daily wear.
Care
Soapy water and a soft brush; ultrasonic is usually safe for heated stones but not for filled ones.
Ruby
- Colour
- Red to pinkish red
- Hardness (Mohs)
- 9
- Birth Month
- July
Its Journey From Formation To Today
Ruby begins as corundum, an aluminum oxide mineral colored red by traces of chromium. It forms in several geological environments, including certain metamorphic rocks. Weathering can release crystals into river deposits.
Ancient Indian traditions called ruby the king of precious stones. Myanmar’s Mogok region became famous for fine rubies, while the gem entered royal treasures and cultural traditions that associated red with courage and protection. These were symbolic beliefs, not scientifically established powers.
New deposits in Mozambique reshaped modern supplies. Today laboratories assess natural features, treatments and sometimes geographic origin. Ruby’s fiery color carries centuries of human fascination as well as a much older geological story.
Meaning
Passion, courage and protection; the red variety of corundum, the same mineral as sapphire.
Care
Soapy water and a soft brush; avoid ultrasonic, steam and acids on glass-filled rubies.
Amethyst
- Colour
- Lilac to deep purple
- Hardness (Mohs)
- 7
- Birth Month
- February
Its Journey From Formation To Today
Amethyst often grows in cavities inside volcanic rock. Silica-rich fluids deposit quartz crystals over time, while trace iron and natural radiation can produce the purple color. An ordinary-looking rock may hide an entire chamber of amethyst crystals.
Ancient Egyptians carved amethyst, while Greek traditions associated it with avoiding intoxication—the belief behind its name. Purple gems later appeared in religious and aristocratic jewelry throughout Europe.
Large Brazilian deposits expanded the supply in the nineteenth century. Today remarkable geodes from Brazil and Uruguay share the spotlight with fine jewelry. Amethyst is the story of a crystal grown in darkness and admired in daylight.
Meaning
Calm, balance and clarity; the purple member of the quartz family.
Care
Keep away from prolonged strong sunlight and heat, the colour can fade; clean with warm soapy water.
Citrine
- Colour
- Pale yellow to honey orange
- Hardness (Mohs)
- 7
- Birth Month
- November
Its Journey From Formation To Today
Citrine is the yellow-to-golden variety of quartz. Quartz grows from silica-rich fluids, and color centers associated with iron can give natural citrine its warm hues. Natural yellow citrine is relatively uncommon; much material sold as citrine is heat-treated amethyst or smoky quartz, a treatment that should be disclosed.
Yellow quartz appeared in European jewelry traditions over the centuries, including Scottish adornments and nineteenth-century pieces. Its name is related to words for lemon.
Brazilian sources helped make citrine widely available in the twentieth century. Today it appears in cocktail rings, pendants and earrings. Its history combines geological formation, human taste and the craft of gem treatment.
Meaning
Joy, abundance and energy; a warm-toned quartz.
Care
Warm soapy water and a soft brush; avoid sudden temperature changes and long sun exposure.
Tanzanite
- Colour
- Violet-blue (pleochroic)
- Hardness (Mohs)
- 6–7
- Birth Month
- December
Its Journey From Formation To Today
Tanzanite forms in metamorphic rocks under the heat and pressure associated with geological change in East Africa. This vanadium-bearing variety of zoisite can show different blue, violet and brownish colors when viewed from different directions, a property called pleochroism.
Unlike gems traded for millennia, tanzanite entered modern jewelry history in 1967, when crystals were discovered in northern Tanzania. Tiffany & Co. introduced the name 'tanzanite' in 1968 in honor of its country of origin.
Merelani in Tanzania remains the gem’s sole commercial source. Heat treatment is common and may emphasize its attractive blue-violet hues. Tanzanite’s history is a meeting of ancient geology and a very recent human discovery.
Meaning
Transformation and intuition; a rare stone found only in Tanzania.
Care
Relatively soft and brittle: avoid ultrasonic, steam and heat shocks, protect from knocks; choose protective settings for everyday rings.
Aquamarine
- Colour
- Pale blue to sea blue
- Hardness (Mohs)
- 7,5–8
- Birth Month
- March
Its Journey From Formation To Today
Aquamarine does not come from the sea. It often crystallizes in granitic pegmatites, where late-stage mineral-rich fluids can grow large beryl crystals. Trace iron gives aquamarine its pale blue to sea-blue colors.
The name comes from Latin words meaning sea water. In ancient maritime traditions blue stones were associated with safe voyages, while European artisans used aquamarine for decorative carvings and jewelry.
Brazil’s Minas Gerais region later became celebrated for fine aquamarine crystals, joined by sources in Africa and Asia. Modern cutters favor shapes that showcase clarity and color. It is a gem born in rock that evokes the ocean.
Meaning
Serenity, courage and clear communication; blue beryl, the sister of emerald.
Care
Soapy water and a soft brush; protect from hard knocks.
Onyx
- Colour
- Black or black-and-white banded
- Hardness (Mohs)
- 6,5–7
- Birth Month
- Not on the modern list
Its Journey From Formation To Today
Onyx is a banded variety of chalcedony, made of microscopic quartz crystals. Silica-rich solutions deposit thin layers inside cracks and cavities, sometimes forming striking parallel bands. Its pattern is a record of repeated geological growth.
Greek and Roman craftspeople used banded stones for seals and carved cameos. By cutting through differently colored layers, artists brought tiny portraits and scenes into relief. The art flourished again in Renaissance Europe.
Today black onyx is popular in rings and bracelets. Much uniformly black material on the market is dyed chalcedony, an established treatment that should be disclosed. Onyx connects ancient carving traditions with modern minimalist jewelry.
Meaning
Strength, focus and protection; popular in men's jewelry and signet rings.
Care
Keep away from chemicals, perfume and acids; wipe with a damp soft cloth, avoid ultrasonic.
Pearl
- Colour
- White, cream, pink, black
- Hardness (Mohs)
- 2,5–4,5
- Birth Month
- June
Its Journey From Formation To Today
Pearl begins not in deep rock but inside a living mollusk. A pearl sac deposits thin layers of nacre made of aragonite crystals and organic matter. Layer after layer, a pearl takes shape. Fine natural pearls formed without human intervention are exceptionally rare.
For centuries, divers in the Persian Gulf, the Indian Ocean and other waters searched for pearls. The gems entered royal treasures and ceremonial adornments, becoming prized for their soft luster.
At the end of the nineteenth century, Japanese pearl cultivation advanced dramatically. Kokichi Mikimoto produced cultured blister pearls in 1893, and improved methods helped make round cultured pearls widely available during the twentieth century. Modern Akoya, South Sea, Tahitian and freshwater pearls continue this story of nature and skilled cultivation.
Meaning
Purity, elegance and wisdom; an organic gem made by a living mollusc.
Care
Last on, first off: keep away from perfume and cosmetics, wipe with a damp cloth, store separately in a soft pouch.
Lapis Lazuli
- Colour
- Deep blue with golden pyrite flecks
- Hardness (Mohs)
- 5–6
- Birth Month
- Traditional: December
Its Journey From Formation To Today
Lapis lazuli is a rock, not a single mineral. It usually contains blue lazurite together with calcite and sparkling pyrite. It forms in metamorphosed limestone environments, where heat and mineral-rich fluids transform the original rock.
Afghanistan’s Sar-e-Sang mines have supplied lapis for thousands of years. Through ancient trade routes it reached Mesopotamia and Egypt, where it appeared in seals, ornaments and royal objects. Later, carefully processed lapis became the precious ultramarine pigment sought by European painters.
Today lapis is also sourced from places such as Chile and is used in cabochons, pendants and carvings. A single stone can evoke mountain geology, early international trade and the history of art.
Meaning
Wisdom, truth and royalty; a rock prized since ancient Egypt.
Care
Porous and soft: avoid water soaks, chemicals and ultrasonic; wipe with a dry soft cloth.
Peridot
- Colour
- Olive to yellowish green
- Hardness (Mohs)
- 6,5–7
- Birth Month
- August
Its Journey From Formation To Today
Peridot is the gem variety of olivine, a mineral that is a main component of Earth’s upper mantle. Its journey often begins many kilometers underground. Volcanic activity and tectonic movement can carry olivine-bearing rock fragments toward the surface, and olivine also occurs in rare stony-iron meteorites called pallasites.
In ancient Egypt, peridot was mined on Zabargad (St. John’s) Island in the Red Sea and valued for centuries. Because of its green color it was often confused with emerald, and some sources suggest that certain historical “emeralds” may in fact have been peridots. In medieval Europe it adorned religious objects and jewelry.
Today peridot comes from sources such as Pakistan’s Kohistan region, Myanmar, China and Arizona in the United States. Iron in its structure produces the vivid olive to yellowish green. August’s birthstone, peridot is a rare gem story that stretches from the mantle to meteorites.
Meaning
Joy, vitality and renewal; a rare green gem born in the Earth's mantle.
Care
Relatively delicate: avoid ultrasonic, acids and knocks; wipe with warm soapy water and a soft cloth.
Moonstone
- Colour
- White, grey, peach with a blue sheen
- Hardness (Mohs)
- 6–6,5
- Birth Month
- June (alternative)
Its Journey From Formation To Today
Moonstone is a feldspar mineral that forms in igneous and metamorphic rocks, especially coarse-grained pegmatites. As the crystal cools, two feldspar types separate into extremely thin alternating layers. Light scattering within those layers creates a soft floating blue sheen called adularescence.
Accounts attributed to the Roman naturalist Pliny link the stone’s glow to the phases of the moon, and in India it was regarded as sacred. The quarries of Sri Lanka supplied moonstone for centuries. One of its names, “adularia,” is associated with the Adula region of the Alps.
Art Nouveau jewelers around the turn of the twentieth century used moonstone’s milky glow in nature- and moon-inspired designs. Today stones from Sri Lanka, India, Madagascar and Myanmar are usually cut as cabochons to show the sheen at its best. It is one of the alternative birthstones for June.
Meaning
Intuition, new beginnings and calm; known for its adularescent glow.
Care
Soft and prone to cleaving: avoid ultrasonic, chemicals and knocks; wipe with a soft cloth.
Opal
- Colour
- Play of colour on a white to transparent body
- Hardness (Mohs)
- 5,5–6,5
- Birth Month
- October
Its Journey From Formation To Today
Opal is not a crystalline mineral but hydrated amorphous silica. Silica-rich groundwater seeps into cracks and cavities in rock and, over millions of years, deposits tiny silica spheres. In precious opal these spheres are arranged in an orderly way, bending light into shifting “play of color.” The deposits that formed in Australia’s ancient sedimentary rocks make it the world’s most important opal source.
Opal was highly prized in ancient Rome, where Pliny described how it combined the colors of many gems in a single stone. For a long time Europe’s main source was the Červenica deposits in what is now Slovakia. Nineteenth-century discoveries in Australia made opal known worldwide, and fields such as Coober Pedy, Lightning Ridge and Queensland became famous.
Ethiopia’s Welo deposits entered the market around 2008 and added bright, light-bodied opal. Because opal contains water, it is sensitive to sudden temperature changes and drying, which is why its care differs. October’s birthstone, opal is a natural art whose color pattern is unique to each piece.
Meaning
Creativity, inspiration and hope; every stone's play of colour is unique.
Care
Contains water: do not soak, and avoid sudden heat changes, drying out and ultrasonic; wipe with a damp soft cloth.
Garnet
- Colour
- Deep red; also green, orange
- Hardness (Mohs)
- 6,5–7,5
- Birth Month
- January
Its Journey From Formation To Today
Garnet is not a single mineral but a group of minerals sharing a similar crystal structure. Species such as pyrope, almandine, spessartine, grossular and andradite occur in many colors. Garnets typically crystallize in metamorphic environments, where heat and pressure transform rock, and sometimes in igneous rocks. Because they are hard and durable, they can also accumulate in river sands as rocks weather away.
Its name is associated with the Latin “granatus,” because the crystals resemble red pomegranate seeds. Used for beads and ornaments since the Bronze Age, garnet appeared in signet rings and carved stones in ancient Egypt and Rome. In the nineteenth century Bohemia’s deep-red pyrope garnets became a favorite in European jewelry.
Red may be the first color that comes to mind, but garnets also occur in green, orange, yellow and purple tones. Vivid green tsavorite, discovered in East Africa in the 1960s, became a new gem name within the group. January’s birthstone, garnet is loved for its warm color and everyday durability.
Meaning
Passion, loyalty and energy; durable enough for everyday jewelry.
Care
Durable: soapy water and a soft brush are enough; protect from sudden heat changes and hard knocks.
Rose Quartz
- Colour
- Pale pink to rose
- Hardness (Mohs)
- 7
- Birth Month
- Not on the modern list
Its Journey From Formation To Today
Rose quartz is the pink variety of quartz. It typically forms in coarse-grained rocks called pegmatites, during the late stages of crystallization from silica-rich fluids. Trace elements and microscopic inclusions have been proposed as the source of its pink color, which is why the stone is usually slightly cloudy and transparent crystals are rare.
People have worked rose quartz for thousands of years. It is known from beads and seals in Mesopotamia, and from ornaments and carvings in ancient Egypt and Rome. Pink has been linked to love and compassion in many cultures; these meanings are cultural traditions, not scientific properties.
Today Brazil’s Minas Gerais region, Madagascar, India and South Africa are important sources. The stones are mostly cut as cabochons, beads and carvings. With its soft pink tone and calm look, rose quartz is quartz’s most romantic face.
Meaning
Love, compassion and calm; the pink member of the quartz family.
Care
Keep from prolonged strong sunlight, the colour can fade; clean with warm soapy water and a soft cloth.
Swiss Blue Topaz
- Colour
- Vivid sky blue
- Hardness (Mohs)
- 8
- Birth Month
- November (topaz); December (blue topaz) on some lists
Its Journey From Formation To Today
Topaz is a mineral containing aluminum, fluorine and silica. It typically crystallizes from fluorine-rich vapors in cavities of igneous rocks such as granite and rhyolite, and in pegmatites. With a Mohs hardness of 8 it is among the more durable jewelry stones. Natural topaz can be yellow, brown, pink, colorless or pale blue.
Topaz has been valued by many cultures. In the eighteenth century the golden-orange “imperial” topaz found around Ouro Preto in Brazil became famous in Europe, and Russia’s Ural Mountains were another important source.
Natural blue topaz is rare and usually pale. The vivid “Swiss blue” on the market is a trade color obtained by irradiating colorless topaz and then heating it, a common treatment that should be disclosed. The name does not mean the stone comes from Switzerland. Topaz is the birthstone of November, and blue topaz also appears on some lists for December.
Meaning
Calm, clear expression and freshness; its vivid blue is usually produced by treatment.
Care
Hard but can cleave along one direction: avoid hard knocks and sudden heat changes; clean with soapy water and a soft brush.
Frequently Asked Questions
What is the difference between lab-grown and natural diamond?
They are chemically, physically and optically the same: pure carbon with a Mohs hardness of 10. Only the origin differs: natural diamonds form underground over millions of years, lab-grown diamonds in weeks in a laboratory. Lab-grown stones are usually more affordable and their certificate states 'laboratory-grown'.
How do I choose the right stone?
Start with how often it will be worn: hard stones such as diamond, sapphire and ruby are ideal for everyday rings. Then balance colour, clarity, cut and carat against your budget. Softer stones like emerald, tanzanite, pearl and lapis are best in protective settings.
What do IGI and GIA certificates mean?
IGI and GIA are independent gemological laboratories that document a stone's identity and quality (carat, colour, clarity, cut; origin and treatment for coloured stones). On request we produce diamond and lab-grown diamond pieces with IGI or GIA certificates.
How should I clean my gemstone jewelry?
For most stones warm water, mild soap and a soft brush are enough. Avoid ultrasonic and steam cleaning for emerald, tanzanite, pearl, onyx and lapis. Store pieces in separate pouches and have the prongs checked once a year.
Can you make a piece with the stone I choose?
Yes. In our Istanbul Grand Bazaar atelier we make bespoke and private-label (B2B) pieces in 9K–18K gold and 925 silver with the stone of your choice. Contact us via the quote form or WhatsApp.
Talk to our atelier about stone selection and production.