Ocean Kyanite: Blue Mineral Found in Marine Sediments and Beach Sands

What is Ocean Kyanite?

Kyanite is a blue aluminum silicate mineral that often occurs in blade, columnar, or fibrous crystal forms. The name "kyanite" comes from the Greek word "kyanos" meaning blue. One variety of kyanite is called "ocean kyanite" which refers to kyanite crystals or aggregates found in an ocean setting.

Where is Ocean Kyanite Found?

Ocean kyanite is found in beach sands and offshore marine sediments. Deposits have been discovered in areas like Australia, India, Mozambique, South Africa, Brazil, and the United States. The kyanite in these deposits likely originated from metamorphic rocks on land that eroded and washed into the ocean over time.

Wave action and ocean currents spread kyanite-bearing sands along shorelines creating placer deposits rich in kyanite. These ocean kyanite deposits tend to accumulate in areas with swift currents and churning wave action as heavier minerals like kyanite concentrate in areas of active sediment transport.

How Does Ocean Kyanite Form?

Kyanite forms deep underground at high pressure and temperature conditions during the metamorphism process when shale or mudstone is altered by heat and stress. This causes the atoms in clay minerals to rearrange into sheet silicate structures like kyanite.

Over millions of years, ongoing erosion brings deeply buried kyanite deposits closer to the Earth's surface. Eventually, outcrops of kyanite-bearing metamorphic rock become exposed. Further erosion breaks down the outcrops releasing kyanite crystals into rivers and streams.

These river systems transport detached bits of kyanite out to sea. Wave action spreads the heavy kyanite grains along the shoreline while tides and currents diffuse and concentrate kyanite offshore. These combined geological processes allow "ocean kyanite" placer deposits to form.

Properties of Ocean Kyanite

Color

The most distinctive property of kyanite is its vibrant blue color. Ocean kyanite ranges from a pale sky blue to deep azure tones. Most blue ocean kyanite is translucent with a vitreous to pearly luster.

Hardness & Durability

Kyanite has a hardness of 4.5 to 7 on the Mohs hardness scale which means ocean kyanite aggregates can withstand abrasion during shoreline transport without much breakdown. Its elongated blade-shaped crystals resist fracturing making kyanite more durable than other lighter minerals.

Density & Specific Gravity

The specific gravity of kyanite ranges from 3.6 to 3.7 which means the mineral is quite dense compared to common minerals making up beach sand like quartz and feldspar. This allows ocean currents to readily transport dense kyanite grains great distances.

Uses & Applications

Abrasives

The hardness, durability, and resistance to heat of ocean kyanite make it useful as an abrasive. Kyanite sands are used for grinding and polishing in applications ranging from metalsmithing to woodworking. Softer grades also see some use in abrasive blasting for surface preparation.

Refractory Materials

High heat resistance and low thermal expansion make kyanite a suitable refractory material. Ocean kyanite aggregates serve well as linings in furnaces and kilns used for firing ceramics or smelting metal. Kyanite also sees use in refractory brick, heat shields, and ceramic ware.

Jewelry

Gem dealers sometimes facet ocean kyanite into beads and cabochons to take advantage of its brilliant blue colors. Tumbled or rough chunks of ocean kyanite also make interesting looking beads for jewelry. Occasionally, translucent blue kyanite may be of high enough quality to facet into gemstones.

While not as extensively used as metamorphic or commercial synthetic kyanite, ocean deposits still constitute a functional source of this unique mineral that generates interest among collectors and hobbyists.

FAQs

Where can I find ocean kyanite?

Ocean kyanite deposits occur globally in beach sands and marine sediments. Significant deposits have been found in Australia, India, Mozambique, South Africa, Brazil and parts of the United States.

What causes the blue color in kyanite?

Trace amounts of the transition metal chromium get trapped in the crystal lattice structure of kyanite during its formation, causing kyanite's distinctive blue hue.

Is kyanite expensive?

While fine gem-quality kyanite can be quite valuable, commercial mineral grades and raw ocean kyanite aggregates are abundantly available and affordable.

Is ocean kyanite used in industry?

Yes, ocean kyanite's hardness and heat resistance allow it to serve well as an abrasive material or refractory liner in high wear and temperature applications.