Gemstones and gem materials that start with O include obsidian, ocean jasper, oligoclase, olivine, onyx, opal, opalite, orange calcite, orbicular jasper, Oregon sunstone, Orthoceras fossil, orthoclase, Ouro Verde quartz and Owyhee opal.
This directory includes natural minerals, ornamental rocks, volcanic glass, fossil material, treated quartz and manufactured glass.
Traditional gemstone meanings are symbolic associations rather than scientifically proven medical effects.
Continue from Gemstones That Start With N. For a broader specimen-focused directory, explore Crystals That Start With O.
O Gemstones at a Glance
| Gemstone or material | Typical appearance | Material type | Common use |
|---|---|---|---|
| Obsidian | Black or patterned volcanic glass | Natural glass | Cabochons, beads and carvings |
| Ocean Jasper | Multicolored circular and orbicular patterns | Chalcedony-rich lapidary material | Cabochons and beads |
| Oligoclase | White, yellow, green or iridescent | Plagioclase feldspar | Faceted gems and cabochons |
| Olivine | Yellow-green to olive green | Mineral group | Faceted peridot and specimens |
| Onyx | Black, white or straight-banded chalcedony | Chalcedony | Rings, cameos and cabochons |
| Opal | White, black, transparent or multicolored | Hydrated silica | Rings, pendants and earrings |
| Opalite | Milky blue or orange-glowing glass | Manufactured glass | Beads and fashion jewelry |
| Orange Calcite | Peach, orange or honey-colored | Carbonate mineral | Carvings and protected pendants |
| Orbicular Jasper | Circular, eye-like or rounded patterns | Patterned silica-rich material | Cabochons and beads |
| Oregon Sunstone | Peach, red, green or color-changing | Feldspar gemstone | Faceted and cabochon jewelry |
| Orthoceras Fossil | Dark matrix with pale fossil outlines | Fossil-bearing carbonate rock | Pendants and carvings |
| Orthoclase | White, pink, yellow or colorless | Potassium feldspar | Faceted gems and cabochons |
| Ouro Verde Quartz | Bright yellow-green quartz | Treated quartz | Faceted fashion jewelry |
| Owyhee Opal | Pale blue to blue-gray common opal | Opal variety | Cabochons and pendants |
Obsidian
Obsidian is natural volcanic glass formed when silica-rich lava cools too quickly to develop a crystalline structure.
It commonly appears:
- Black.
- Brown.
- Mahogany patterned.
- Snowflake patterned.
- Golden or silver sheen.
- Rainbow colored under directional light.
Obsidian is traditionally associated with protection, self-awareness and recognizing uncomfortable truths.
It is widely used for:
- Cabochons.
- Beads.
- Pendants.
- Carvings.
- Decorative blades and points.
Obsidian takes a smooth polish but can break into extremely sharp edges. Rings and bracelets should use settings that protect exposed corners.
Ocean Jasper
Ocean jasper is a commercial lapidary name associated with colorful orbicular chalcedony from Madagascar.
Its patterns may include:
- Circles.
- Eyes.
- Wavy bands.
- Spots.
- Flower-like shapes.
- Small crystal-lined cavities.
Common colors include green, pink, cream, yellow, red, brown and gray.
Ocean jasper is traditionally associated with patience, optimism and adapting to gradual change.
Solid material works well in pendants, beads and cabochons. Pieces with open cavities or thin orbicular areas should be protected from impact and trapped cleaning residue.
Oligoclase
Oligoclase is a member of the plagioclase feldspar series.
Gem and collector material may appear:
- White.
- Colorless.
- Pale yellow.
- Greenish.
- Gray.
- Iridescent or aventurescent.
Some sunstone materials fall within or near the oligoclase compositional range.
Oligoclase is traditionally associated with adaptability, confidence and adjusting plans without losing direction.
Its mineral relationships are explained in the feldspar guide.
Feldspar cleavage makes oligoclase vulnerable to sharp impacts. Protected earrings and pendants are generally safer than exposed everyday rings.
Olivine
Olivine is a mineral group commonly found in igneous rocks, mantle-derived material and some meteorites.
Its colors range from:
- Yellow-green.
- Olive green.
- Brownish green.
- Nearly colorless.
- Deep forest green.
Gem-quality transparent olivine is known as peridot.
Olivine is traditionally associated with renewal, generosity and releasing unproductive resentment.
Transparent material may be faceted, while rough crystals and olivine-rich rocks are collected as specimens.
Olivine is vulnerable to acids and can be brittle. Jewelry should be protected from hard impacts and rapid temperature changes.
Onyx
Onyx is traditionally defined as chalcedony with straight, parallel bands.
Natural and commercial onyx may appear:
- Black and white.
- Brown and white.
- Red-brown and white.
- Uniform black after treatment.
- Green under broader trade usage.
Onyx is traditionally associated with discipline, stability and clear personal boundaries.
It is commonly used for rings, cameos, beads, cabochons and carved objects.
Much black onyx is dyed or treated to create an even color. This is widely accepted when disclosed.
Onyx vs. Obsidian explains how crystalline chalcedony differs from natural volcanic glass.
Opal
Opal is hydrated silica that may be transparent, translucent or opaque.
Major categories include:
- Precious opal with play-of-color.
- Common opal without play-of-color.
- White opal.
- Black opal.
- Fire opal.
- Boulder opal.
- Hydrophane opal.
- Assembled doublets and triplets.
Opal is traditionally associated with creativity, individuality and emotional expression.
Its care requirements vary considerably. Some opals absorb water, while others are stabilized, smoked, dyed or assembled.
Color, pattern, brightness, body tone, stability and treatment influence the values discussed in the opal price guide.
Opalite
Opalite is usually manufactured glass with a milky blue appearance and an orange or golden glow when held against light.
It is traditionally associated with:
- Openness.
- Adaptability.
- Communication.
- Transition.
- Gentle self-expression.
Opalite is not natural opal.
It is commonly made into:
- Beads.
- Cabochons.
- Pendants.
- Small carvings.
- Fashion rings.
Glass can scratch and chip, especially around drilled holes and thin edges. Sellers should identify opalite as manufactured material rather than a rare natural crystal.
Orange Calcite
Orange calcite ranges from pale peach and apricot to vivid orange and honey-colored tones.
It may appear:
- Transparent.
- Translucent.
- Cloudy.
- Banded.
- Waxy when polished.
Orange calcite is traditionally associated with motivation, creativity and bringing energy to unfinished tasks.
It is commonly carved or polished into beads, cabochons and decorative objects.
Calcite is soft and reacts with acids. Orange calcite should be kept away from vinegar, citrus juice, abrasive cleaners and harder stones.
Orbicular Jasper
Orbicular jasper is a broad lapidary term for silica-rich material containing rounded, eye-like or circular patterns.
Its colors can include:
- Green.
- Red.
- Brown.
- Cream.
- Yellow.
- Pink.
- Gray.
Orbicular jasper is traditionally associated with wholeness, patience and steady progress.
The name may cover materials from different deposits with varying composition. Locality and seller disclosure are therefore helpful.
Most solid material is suitable for cabochons, beads and casual jewelry, although open cavities and weak matrix require protection.
Oregon Sunstone
Oregon sunstone is a feldspar gemstone associated with deposits in Oregon, United States.
Its colors include:
- Colorless.
- Pale yellow.
- Peach.
- Orange.
- Red.
- Green.
- Bicolored or color-changing combinations.
Some stones display copper-related aventurescence or visible copper platelets.
Oregon sunstone is traditionally associated with independence, confidence and recognizing worthwhile opportunities.
Transparent material may be faceted, while included stones are frequently cut as cabochons.
Feldspar cleavage makes protection from sharp blows important, particularly in rings.
Orthoceras Fossil
Orthoceras fossil is a commercial name used for polished rock containing elongated shells of ancient straight-shelled cephalopods.
The material commonly shows:
- Pale fossil outlines.
- Dark limestone matrix.
- Chambered internal patterns.
- White, gray or cream sections.
It is traditionally associated with perspective, endurance and respect for natural history.
Orthoceras material is fossil-bearing rock rather than a mineral crystal. It belongs among the organic-origin and fossil materials explained in Types of Gemstones.
The carbonate-rich matrix can be damaged by acids. Coatings, fillers and reinforcement should be disclosed.
Orthoclase
Orthoclase is a potassium feldspar mineral that may occur in:
- White.
- Cream.
- Pink.
- Yellow.
- Colorless.
- Gray.
Transparent yellow orthoclase can be faceted, while opaque or included material may be polished into cabochons.
Orthoclase is traditionally associated with organization, structure and practical judgment.
It has two prominent cleavage directions. Earrings and pendants are generally safer than rings exposed to repeated knocks.
Some moonstone material is associated with potassium feldspar compositions closely related to orthoclase.
Ouro Verde Quartz
Ouro Verde quartz is bright yellow-green quartz whose commercial color is generally produced through irradiation and heat treatment.
Its appearance may range from:
- Lemon green.
- Neon yellow-green.
- Golden chartreuse.
- Bright transparent lime tones.
Ouro Verde quartz is traditionally associated with optimism, confidence and visible self-expression.
It belongs to the wider quartz family.
The treatment should be disclosed because the vivid color does not represent ordinary untreated quartz. The material has quartz-level scratch resistance but can still chip at facet edges after impact.
Owyhee Opal
Owyhee opal is a pale blue to blue-gray common opal associated with Oregon.
It is usually:
- Opaque to translucent.
- Soft sky blue.
- Blue-gray.
- Evenly colored or lightly clouded.
- Without strong play-of-color.
Owyhee opal is traditionally associated with calm communication, patience and quiet reflection.
The material can be porous and may lose color or develop cracks under unsuitable conditions.
Avoid prolonged soaking, rapid drying, strong heat, perfume and household chemicals.
Which O Gemstones Are Best for Jewelry?
More practical choices include:
- Onyx.
- Obsidian.
- Ocean jasper.
- Orbicular jasper.
- Oregon sunstone.
- Orthoclase in protected settings.
- Olivine gem varieties.
- Ouro Verde quartz.
Materials requiring more protection include:
- Opal.
- Owyhee opal.
- Orange calcite.
- Oligoclase.
- Orthoceras fossil.
- Opalite glass.
Scratch resistance is only one part of durability. Cleavage, toughness, porosity and treatments also affect wearability, as explained in Gemstone Toughness vs. Hardness.
Care Guide for O Gemstones
- Protect obsidian from edge impacts that can create sharp chips.
- Check ocean and orbicular jasper for cavities before soaking.
- Keep feldspar gems away from sharp blows.
- Avoid acids on orange calcite and fossil-bearing carbonate rock.
- Clean opal according to its exact type and treatment.
- Treat opalite as glass rather than natural opal.
- Keep Owyhee opal away from prolonged moisture and rapid drying.
- Ask how Ouro Verde quartz acquired its color.
- Avoid steam and ultrasonic cleaning when fractures, coatings or assembled layers are present.
Frequently Asked Questions
What is the most valuable gemstone that starts with O?
Fine precious opal can be the most valuable, especially stones with bright play-of-color, desirable patterns and stable natural body color.
Which black gemstones start with O?
Obsidian, black onyx and black opal are the best-known examples.
Is opalite a natural gemstone?
Most opalite sold in jewelry is manufactured glass.
Is olivine the same as peridot?
Peridot is the gem-quality transparent variety of olivine.
Is Orthoceras fossil a crystal?
No. It is fossil-bearing rock commonly polished for jewelry and decorative use.
Is Oregon sunstone naturally colored?
Yes, natural stones occur in several colors. Copper inclusions can create red, green or sparkling effects in some material.
Is Ouro Verde quartz natural?
The quartz is natural, but its vivid yellow-green commercial color is generally produced through treatment.
Can opal be worn every day?
It can be worn regularly in protective settings, but it requires more careful handling than sapphire, diamond or garnet.
Continue the Gemstone Alphabet
Continue with Gemstones That Start With P, or browse all alphabetical directories through the Crystals 101 collection.
