Uncoiling the Secrets of Serpentine: Nature’s Marvelous Green Gem

Serpentine is a group of minerals that share similar physical properties and geological origins. The most common serpentine minerals are antigorite, chrysotile, and lizardite. These minerals form through a process called serpentinization, which occurs when ultramafic rocks like peridotite and dunite are altered by heat and water.

The most striking feature of serpentine minerals is their distinctive green color. They also often display an attractive patterned appearance and have a characteristically slippery, greasy feel. In addition, serpentine minerals tend to be translucent. Their other diagnostic physical properties include a white streak, a hardness ranging from 3 to 6 on the Mohs scale, a specific gravity of 2.5-2.6, and a chemical composition rich in magnesium, iron, and silica.

Serpentine has a variety of uses stemming from its unique properties. Historically, it was prized as a source of asbestos, although this application has declined due to health concerns. It remains commercially important as a source of magnesium. Serpentine is also valued as a decorative architectural stone and in lapidary work as a gemstone. Recently, it has seen increased popularity for its believed metaphysical healing properties.

What is Serpentine?

Serpentine refers to a group of rocks that are composed of one or more serpentine group minerals. These minerals share a similar chemical composition and crystal structure. The most common types of serpentine minerals are antigorite, chrysotile, and lizardite. These three minerals make up about 95% of all serpentine found in nature.

Some key identifying features of serpentine are its greenish color, attractive patterned appearance, and greasy or waxy feel. The vibrant green hues are caused by the presence of iron in the mineral’s chemical structure. Serpentine also has a translucent diaphaneity, meaning light can partially travel through it.

Other diagnostic physical properties of serpentine include:

• Streak: White
• Luster: Greasy or waxy
• Hardness: 3 to 6 on Mohs hardness scale
• Specific Gravity: 2.5 to 2.6
• Crystal System: Monoclinic
• Chemical Composition: Magnesium iron silicate hydroxide [(Mg,Fe)3Si2O5(OH)4]

How Does Serpentine Form?

Serpentine forms through a process called serpentinization, which occurs when ultramafic rocks like peridotite and dunite are altered by heat and water. This interaction causes the original minerals olivine and pyroxene to break down and reform into serpentine minerals.

Serpentinization typically takes place at mid-ocean ridges where mantle rock is exposed to seawater circulating through the oceanic crust. It also occurs in certain mountain belts where blocks of oceanic lithosphere get pushed up and exposed to metamorphic fluids. The conditions needed are high heat flow, available water, and fractured ultramafic rock.

As the serpentinization process takes place, the volume of the original rock expands, its density decreases, and its strength and rigidity decline. This can lead to weaknesses and deformation in the surrounding rock. Magnesium, silica, and water are introduced, while iron and other elements are leached out.

Varieties of Serpentine

There are over 20 unique members of the serpentine group, but only a few major varieties.

Chrysotile

Chrysotile, also known as white asbestos, is the fibrous form of serpentine. Its long, thin fibers made it desirable for industrial purposes, but inhalation of asbestos fibers is now known to cause lung disease. Most uses of chrysotile have been discontinued.

Antigorite

Antigorite is the most abundant and important type of serpentine. It occurs in corrugated plates or fibers and has a hardness of about 5.5. The antigorite form of serpentine does not present safety concerns and is frequently used as a gemstone.

Lizardite

Lizardite is a fine-grained, platy variety of serpentine. It is translucent to opaque with a hardness ranging from 3 to 4. Lizardite is usually green in color.

Other minor varieties include amesite, cronstedtite, fraipontite, nepouite, and williamsite. These types are rare and of minimal economic value.

Comparison of Serpentine with Other Rocks

Rock	Composition	Hardness	Uses	Colors	Texture
Serpentine	Magnesium silicate hydroxide	3-6	Gemstone, asbestos source, architectural stone, metaphysical healing	Green, brown, yellow, white, black	Smooth, greasy
Granite	Quartz, feldspar, mica	6-7	Construction, monuments, countertops	White, pink, gray	Coarse-grained
Marble	Metamorphosed limestone	3-4	Sculpture, architecture, tiles	White, black, pink, gray	Fine- to coarse-grained
Slate	Metamorphosed shale	3-4	Roofing, flooring, chalkboards	Black, gray, green, purple	Fine-grained, foliated
Quartzite	Metamorphosed quartz sandstone	7	Concrete aggregate, ornamental stone	White, pink, yellow, red	Granular
Soapstone	Talc and other minerals	1-2	Countertops, carvings, ornaments	Gray, brown, green, black	Fine-grained
Obsidian	Volcanic glass	5-6	Arrowheads, sculpture, gemstone	Black, brown, gray, green	Smooth, glassy
Sandstone	Cemented quartz grains	4-7	Building stone, oil reservoirs	White, yellow, red, brown	Clastic, porous

In summary, serpentine is moderately soft and often green or brown with a greasy texture. It occupies a unique niche among rocks based on its chemical composition, modes of formation, and practical uses over time. While sharing some attributes with other stones, serpentine is distinctive.

Where is Serpentine Found?

Serpentine is abundant and found in many localities around the world. Some major deposits include:

• Canada – Thetford Mines, Quebec is a leading asbestos and serpentine producer.
• United States – California, Vermont, Pennsylvania, Maryland, and Texas have serpentine deposits.
• South Africa – The Northern Cape Province hosts asbestos and serpentine mining operations.
• China – Xiuyan, Liaoning Province has major serpentine reserves.
• Italy – Valmalenco is renowned for its brilliant green serpentinite rock.
• England – The Lizard peninsula in Cornwall has extensive serpentinization.
• New Zealand – Major serpentine belts run through both main islands.

In these areas, you can often find serpentine in association with other metamorphic minerals like olivine, magnetite, and chromite. Alpine metamorphic belts frequently contain bodies of serpentinized ultramafic rock as well.

Uses of Serpentine

Decorative and Architectural Stone

Serpentine has served as a decorative stone for thousands of years. The Romans used colorful serpentinite for ornamental objects. Today it is still popular as an architectural stone for features like fireplace mantles, wall tiles, and window sills.

Serpentine is suitable for this use because it polishes to a nice luster, works easily, and comes in a range of attractive green shades. Sometimes it exhibits unique patterns like veining or mottling that add visual interest.

Asbestos

The fibrous variety chrysotile has been used commercially as asbestos. Asbestos fibers are flame and heat resistant, as well as strong and lightweight. This led to asbestos being widely applied as insulation and fireproofing. It was also blended into cements, tiles, plasters, and fabrics.

However, by the late 1900s, asbestos was found to be a health hazard if inhaled. Breathing in tiny fibers can cause lung scarring and cancer. Most countries have now banned the use of asbestos products.

Gemstone Material

While not a traditional precious gemstone, some varieties of serpentine are used as an ornamental stone in jewelry. Serpentine’s olive greens and browns, smooth texture, and affordability make it suitable for crafting cabochons, beads, and small sculptures. These may be mistaken for jade by the casual observer.

Other gem-quality serpentine comes from the bowenite variety. Its rich greens, hardness and durability allow bowenite to be fashioned into beads, brooches, rings, and even limited edition carvings.

Metaphysical and Alternative Healing

In recent years, serpentine has become popular in the metaphysical community. It is believed to hold therapeutic properties that can stimulate the heart chakra, clear blocked energies, and promote inner peace.

Some alternative practitioners utilize serpentine in crystal healing sessions. These are intended to bring harmony and well-being to the mind, body, and spirit.

Others carry or wear serpentine jewelry to purportedly guard against negative influences or sorcery. Small ornamental carvings made of serpentine can also carry metaphysical meaning.

Other Industrial Uses

Serpentine has some additional industrial and commercial applications, including:

• A source of magnesium for chemical manufacturing
• A soil additive used to enhance plant growth
• A filler in paints, putties, and plastics
• An absorbent for oils and greases

Are All Serpentines Equally Safe?

While most types of serpentine are considered harmless, asbestos-bearing serpentine does pose health risks. Only chrysotile has the thin, curved asbestos fibers that can cause lung disease when airborne particles are inhaled.

Other serpentine group minerals do not naturally form these hazardous fibers. Both antigorite and lizardite serpentine are regarded as non-toxic and safe to handle and work.

Care should always be taken during serpentine processing, cutting, or polishing to minimize and properly contain any incidental dust. Opt for wet cutting methods when possible. With reasonable precautions, serpentine can be used without significant safety concerns.

Notable Localities

Some of the world’s most important and noteworthy serpentine deposits include:

Thetford Mines, Quebec, Canada

Thetford Mines was once the largest asbestos mining region in North America. For over 100 years, high-grade chrysotile was extracted and processed here. Though mining ceased in 2012, Thetford Mines remains a significant location for studying serpentinization geology.

Valmalenco, Lombardy, Italy

In this Alpine valley, brilliantly colored serpentinite rock is omnipresent. For centuries, the vivid green stones have been used by artisans. Valmalenco serpentine crafts are still prized today as ornamental treasures.

State of California, USA

California designated serpentine as its official state rock in 1965. This was due to California’s extensive serpentine deposits and their importance to regional geology. The California State Gemstone is even benitoite contained in serpentine.

Lizard Peninsula, Cornwall, England

The Lizard Peninsula hosts one of the largest serpentine bodies in Great Britain. Here, the ocean floor was thrust upward and then extensively serpentinized. Its rocky headlands contain diverse serpentine minerals.

Xiuyan, Liaoning Province, China

The ultramafic intrusion here contains China’s major supply of antigorite asbestos and serpentinite. These have been extensively mined since the deposit’s discovery in the 1930s.

Frequently Asked Questions about Serpentine

What causes the green color in serpentine?

The green hues of serpentine are caused by the presence of iron in the mineral’s chemical structure. Specifically, ferrous iron (Fe2+) produces the vibrant green shades.

Is serpentine a metamorphic rock?

Yes, serpentine is a metamorphic rock that forms when ultramafic rocks like peridotite are altered through hydrothermal metamorphism. This process is called serpentinization.

What is the hardness of serpentine on the Mohs scale?

Serpentine has a variable hardness typically between 3 and 6 on the Mohs hardness scale. Softer varieties like lizardite may be 3, while harder forms like antigorite may reach 5 or 6.

Where are some major serpentine deposits located?

Major deposits are found in Canada (Quebec), South Africa, China, United States (California, Vermont), Italy (Valmalenco), England (Cornwall), and New Zealand.

What is the crystal structure of serpentine minerals?

Most serpentine group minerals crystallize in the monoclinic crystal system. This means they form three unequal axis angles and unequal side lengths.

Is serpentine valuable?

While not very valuable monetarily, serpentine is considered a commercially useful industrial mineral. Historically it was treasured for asbestos. Today it is more prized for decorative uses.

What is bowenite?

Bowenite is a varietal name for hard, dense serpentine that takes a good polish. It is used as an ornamental gemstone for limited jewelry purposes.

Is serpentine safe to handle?

Chrysotile asbestos bearing serpentine can be hazardous if inhaled. However, most antigorite and lizardite serpentines are considered non-toxic and safe with reasonable precautions taken.

Can someone be allergic to serpentine?

Serpentine does not commonly cause allergic reactions. However, some sensitivities to nickel or chromium traces in serpentine could theoretically occur. Reactions are very rare.

Conclusion

From the architectural grandeur of Rome to the metaphysical healing parlors of today, serpentine has remained alluring for millennia. Though once prized for its asbestos, improved scientific understanding has revealed both the benefits and dangers of this intriguing rock. Serpentine continues to offer ornamental beauty, industrial usefulness, and geological insights to those who search for and study it. Whether cursing it as a troublesome bedrock or praising it as a healing crystal, the allure of serpentine endures.