There are a few different mineral stones that can display blue coloration. The most common blue mineral stones include sapphire, lapis lazuli, azurite, and blue quartz. The blue color in these stones is caused by trace elements and impurities within the mineral’s crystal structure. Identifying which mineral a blue stone belongs to requires an understanding of its physical properties and chemical composition.
Sapphire
Sapphire is one of the most coveted and precious blue gemstones. It gets its vivid blue hue from traces of iron and titanium within its crystalline structure. Sapphire is a variety of the mineral corundum, which is composed of aluminum oxide. Corundum is known for its hardness—it is the second hardest natural mineral after diamond. The Mohs hardness scale ranks sapphire at 9 out of 10. This extreme hardness makes it very durable and resistant to scratching. Sapphire deposits are found in metamorphic rock and igneous rock formations around the world. Notable sapphire sources include Australia, Sri Lanka, Thailand, and Montana in the United States. Besides blue, sapphire is also found naturally in yellow, pink, orange, green, purple, and black color variations depending on the presence of other trace elements.
Lapis Lazuli
Lapis lazuli is a deep blue metamorphic rock composed mainly of the minerals lazurite, calcite, and pyrite. Lazurite is responsible for the vibrant blue color, while pyrite gives it a sparkly, gold-flecked appearance. Lapis lazuli has been prized as a gemstone for thousands of years. It has been mined from the Badakhshan province of Afghanistan as early as the 7th millennium BC. The intense blue stone was highly valued in ancient Egyptian, Mesopotamian, Chinese, and Indian civilizations. They used it frequently in jewelry, carvings, and mosaics. Besides ornamental uses, lapis lazuli was also ground up into a pigment called ultramarine to produce blue oil paint and dye. The best quality lapis lazuli is an evenly colored, deep blue with few white calcite streaks.
Azurite
Azurite is a soft, vivid blue copper mineral produced by the weathering of copper ore deposits. Its chemical composition consists of hydrous copper carbonate. The blue color results from the presence of copper. Azurite is formed in oxidized zones of copper lode deposits and often occurs together with malachite. Notable occurrences are found in the copper mines of Australia, France, Mexico, Morocco, Namibia, and the southwestern United States. Azurite was used as a blue pigment in antiquity. However, it has poor opacity and easily turns into green malachite over time. While azurite itself is too soft for jewelry use, it is sometimes used as cabochon beads. Dark blue azurite against a green malachite background is highly desirable.
Blue Quartz
While ordinary quartz is colorless and transparent, blue quartz is a rare and beautiful natural gemstone. It acquires its soft blue color from microscopic inclusions of blue mineral particles such as dumortierite or tourmaline. The shade can range from very pale blue to deep blue. Most blue quartz crystals and geodes are found in Madagascar and Brazil. Some types of blue quartz include:
| Blue quartz variety | Color origin |
| Dumortierite quartz | Inclusions of the mineral dumortierite |
| Tourmalinated quartz | Needle-like inclusions of blue tourmaline |
| Sodalite-bearing quartz | Patches and streaks of blue sodalite |
While blue quartz can be used for jewelry, most pieces are often carved into ornamental objects and spheres. They are sometimes sliced into plates and polished as ornamental stones in feng shui applications.
Identifying Raw Blue Stones
Raw blue mineral specimens that have not yet been cut or polished can be difficult to identify. Here are some tips for distinguishing between unworked pieces of sapphire, lapis lazuli, azurite, and blue quartz:
- Sapphire has an extremely hard, glassy surface and feels smooth. Natural sapphire geodes have well-defined hexagonal crystal shapes.
- Lapis lazuli feels coarser than glass with visible flecks of pyrite. It leaves a blue streak when scraped against porcelain.
- Azurite often displays botryoidal masses and crusts of deep blue. It feels smooth but leaves blue powder when scraped.
- Blue quartz typically has an elongated, prismatic crystal habit. It may show translucent areas and surface flaws.
Testing hardness, examining inclusions, checking for electrical conductivity, and using chemical tests can also help identify the type of blue mineral.
The Value of Blue Gemstones
Blue is a precious color in gemstones. Here is an overview of the value factors for the main blue stones:
Sapphire
Sapphire value is determined by:
- Color—Intense medium blue commands the highest price. Greenish or grayish blue is less desirable.
- Clarity—Transparent stones with few inclusions are most valuable.
- Cut quality—Well-cut stones showcase better brilliance.
- Carat weight—Larger stones are exponentially more valuable.
- Source—Sapphires from Kashmir and Burma (Myanmar) fetch premium prices.
The most coveted variety of sapphire is the elusive, velvety, cornflower blue variety known as Kashmir sapphire which can reach up to $5,000-20,000 per carat.
Lapis Lazuli
Top grade lapis lazuli is valued for its:
- Vivid blue color—Deeper and more intense blue is better.
- Absence of white calcite—Less calcite indicates better quality.
- Finer grain size—Smaller grains result in a more uniform color.
- Afghan origin—The best historical source is the Sar-e-Sang mines in Afghanistan.
Lapis lazuli prices range greatly depending on quality factors. Top grade lapis can cost $100-500 per ounce of rough stone.
Azurite
Azurite value is based on:
- Color saturation—Rich, deep blue commands higher prices.
- Larger specimen size—Bigger clusters have more visual impact.
- Formation habit—Interesting botryoidal and tabular formations are desirable.
- Associated minerals—Combinations with malachite, chrysocolla, or cuprite add value.
Natural azurite mineral specimens can range from $5 per ounce up to $30 for rare museum-quality pieces.
Blue Quartz
Blue quartz is valued by:
- Intensity of blue color—Pale blue is less desirable than deep blue.
- Translucency—Clear, see-through areas increase value.
- Being unheated—Naturally blue stones are worth more than treated ones.
- Being untreated—Coating and dyeing decrease value.
- Lapidary uses—Cabochons, carvings, and spheres are quite popular.
Fine quality natural blue quartz gems sell for $50-300 per carat. Exceptional pieces over 100 carats can fetch over $1,000 per carat.
Conclusions
The most prominent blue mineral stones that exist in nature include sapphire, lapis lazuli, azurite, and blue quartz. Their blue coloration originates from the presence of certain elemental impurities and structural defects. Identifying raw blue minerals involves examining their physical properties and features. Blue gemstones command high values, with fine sapphires being the most precious. When evaluating blue stones, color intensity, clarity, cut quality, and source locality are the main factors that influence their desirability and price.
