Fiery Green Gems - Hawaiian Peridot's Volcanic Origins and Paradise Hunting Grounds

The Brilliant Green Gems of Hawaii's Peridot Sand Beaches

The fiery green gems known as peridot have a long history intertwined with the volcanic origins of the Hawaiian Islands. Formed deep within the Earth's mantle, trace amounts of the mineral olivine are brought to the surface through eruptions and volcanic processes over countless millennia. As the iron-rich olivine weathers and alters near the surface, gems known as peridot are created. The vivid green color comes from the iron content in the mineral. Many of these peridot gems accumulate along Hawaii's famous green sand beaches, making them a paradise for gem hunters. Let's explore the unique origins and beachy habitats of Hawaiian peridot.

Molten Origins in the Mantle

Peridot gems originate deep underground in the mantle layer that sits just above the Earth's core. Here, extreme heat and pressure squeeze and fold rocks slowly over time. The dominant rock type in the mantle is peridotite, made up of the mineral olivine along with other iron- and magnesium-rich minerals. Peridotite forms at depths from 50-400 miles (80-640 km) underground where temperatures can reach more than 3000°F (1650°C).

Over millions of years, convective forces bring nuggets of peridotite closer to the surface where oceanic plates or continental plates sit above subduction zones. The peridotite reacts with hot water to transform into serpentinite. Fractures and weak zones allow the serpentinite to rise even closer to the crust. Here, at shallower depths and cooler temperatures, the mineral olivine crystallizes within the serpentinite. Rarely, chunks of peridotite or serpentinite rock get broken off and carried all the way up to the surface in magma during volcanic eruptions. These mantle rocks serve as the ultimate source for the peridot crystals and fragments scattered around Hawaii.

Fiery Volcanic Origins

The volcanic processes that built the Hawaiian Islands brought precious peridot to the surface in several ways. As magma from the mantle moved up through fractures miles underground, it sometimes encapsulated small chunks of peridotite. These xenoliths, essentially mantle hitchhikers, get dragged up from great depth by the magma's movement. If they survive the chaotic ride up to the surface, these peridotite xenoliths appear as dark, dense rock fragments sometimes embedded in black lava rock. They serve as literal messengers from the deep Earth.

More commonly, the original olivine crystals carried up get broken down through the violent volcanic activity around and after eruption. Fragments of peridot crystals form,accumulate near vents and rifts, and then get disseminated throughout the eruption area. Much ends up dispersed through basalt lava rock. Finally, when conditions are right, larger rounded crystals form in the remaining magma chambers and pockets deep underground. These can grow over time into large gem-quality peridots that might again get brought up in a future eruption.

Alteration to Peridot

Once on the surface, the olivine fragments and crystals exposed to Hawaii's tropical weather begin transforming through chemical weathering processes. The iron within the olivine alters and oxidizes upon exposure to water and air. When iron is released from the mineral structure, it leaves behind a more silicon-rich and crystalline structure. The final gem-quality crystals are mainly just forsterite, an iron-poor endmember of the olivine solid solution series. These brilliant yellowish-green crystals are classified as the variety of olivine known as peridot.

This alteration process can occur rapidly in Hawaii's climate. On volcanic slopes like Mauna Kea, newly deposited olivine sands can turn completely to peridot gems within decades. Near active rift zones and vents, hot acidic vapors help accelerate the breakdown. Gas bubbles and steam vents associated with the underwater volcano Loihi, Hawaii's youngest volcano, provide ideal conditions for peridot to form rapidly on the seafloor. Eventually waves, currents, and gravity transport the peridot crystals into concentrated accumulations along green sand beaches.

Hawaii's Green Sand Beaches

Thanks to abundant volcanic processes transporting peridot crystals and eroding them into rounded gems on Hawaii's beaches, green sand beaches can be found on several of the islands. The most famous andlargest concentration is Papakōlea Beach (also known simply as Mahana Beach) on the southern tip of the Big Island. The crescent-shaped beach is reachable by hiking in through an adjoining cinder cone volcano. The deep green sand formed by weathered peridot crystals mixed with black lava grains and white coral dust is an incredible sight.

Baby Beach on the eastern tip of Molokai also has an expansive green sand beach thanks to erosion from the nearby East Molokai volcano. Polihale Beach on Kauai and Kaihalulu Beach on Maui also have patches of green sand visible at times. Other less accessible pockets can occasionally be found after winter storms strip away overlying layers, revealing the green gems. Going after big storms and high-energy wave events is the best strategy for finding green sand exposures along Hawaii's rugged and remote coasts.

Hunting for Hawaii's Peridot Gems

For those enchanted by the fiery green glow of peridot gems, the prospect of hunting for these tiny treasures along Hawaii's beaches can become an obsession. As seen on Mahana Beach, the peridot crystals tend to accumulate most in coarse deposits along the high tide line. Here, waves have sorted the dense peridot grains from the other black and white beach sand constituents. The best areas have concentrations ranging from 10% to as high as 80% peridot by volume.

Small plastic bags allow collectors to scoop up handfuls of the green-coated sand for closer inspection. Carefully shaking, blowing, and picking through the sand reveals hundreds of tiny peridot crystals, many with rounded gem-like shapes. It takes patience to gather just a few containers worth of the highest quality gems scattered through tons of green beach sand. Forest green crystals just a few millimeters wide can have facet-grade clarity and radiance - making the hunt well worth the effort for dedicated beachcombers.

Once exhausted from hours of swirling green sand and picking out tiny gems by hand, the remaining bags of peridot crystal concentrates provide pure enjoyment. Set some in a clear glass bowl with light shining from below to appreciate the candy-like glow of high-quality Hawaiian peridot. These volcanic gifts of the islands create a lifetime of memories for those who experience the thrill of the hunt.

Conclusion

The fiery green glow of Hawaiian peridot forms an alluring treasure born directly from the volcanic forces that created the islands. These rare and beautiful gems accumulate slowly over time and require patience and persistence to uncover along Hawaii'sfamous green sand beaches. But for those enchanted by the vision of an iridescent green pool of tiny crystals along the rugged volcanic coasts, the thrill of the hunt makes Hawaii the world's capital for this brilliant gem.

FAQs

How do peridots form in Hawaii?

Peridots form from olivine crystals that originated deep in the Earth's mantle and were brought up to the surface by volcanic eruptions. Once exposed to weathering, the iron in the olivine alters and oxidizes, leaving behind the gem-quality peridot crystals.

Where are the best beaches to find peridots in Hawaii?

The best known beach is Papakōlea or Mahana Beach on the Big Island which has deep green sand with a high concentration of peridot crystals. Baby Beach on Molokai and Polihale Beach on Kauai also have significant green sand deposits.

What is the best way to collect peridots on Hawaii's beaches?

Use small plastic bags to scoop up the green-coated sands, then carefully sift through by shaking, blowing, and picking out the tiny gem crystals by hand. Concentrate on the high tide line where waves have sorted the dense peridot grains.

What time of year is best for finding peridots?

During winter storms when big waves strip away layers of sand, revealing concentrations of the green peridot crystals below. So target trips after high-energy storm and wave events.

Are peridots only found in green sand?

Not always - some peridots accumulate in normal tan or black sand beaches near volcanic vents. But green sand beaches have the highest concentrations, making them prime hunting grounds.