Lava’s Hidden Gems: Discovering Olivine and Peridot in Volcanic Fields

For rockhounds and mineral collectors, few experiences are as exhilarating as the hunt for precious gemstones. Among the diverse materials found in volcanic landscapes, olivine and its gem-quality counterpart, peridot, stand out as remarkable specimens. These verdant minerals provide insights not only into geological processes but also into the potential for finding unique treasures.

Understanding Olivine: The Basics

Olivine is a silicate mineral composed primarily of (Mg, Fe)2SiO4, characterized by its olive-green color, which can vary depending on its iron and magnesium content. One of the most interesting aspects of olivine is its formation. It usually crystallizes in high-temperature environments, often found in mafic and ultramafic volcanic rocks.

This mineral is generally classified based on its composition:

Forsterite (Mg2SiO4) – The magnesium-rich end member.
Fayalite (Fe2SiO4) – The iron-rich counterpart.

Olivine is also indicative of the Earths mantle. The mineral is believed to be the primary component of the upper mantle, providing significant insights into mantle composition and behavior.

The Sparkling Gem: Peridot

Peridot is the gem-quality form of olivine and has gained immense popularity in jewelry due to its vibrant green hues and perfect clarity. gem typically ranges in color from yellow-green to olive-green, with deeper greens being more valuable. The presence of iron contributes to its rich coloration, with larger stones tending to exhibit a more intense chromatic saturation.

Most peridot is found in volcanic rocks such as basalt and tephra, typically within tephritic volcanic deposits. Notably, the ancient volcanoes, particularly those located along mid-ocean ridges, are prolific sources of these gemstones.

Perfecting the Hunt: Where to Find Olivine and Peridot

Identifying the right locations can significantly enhance your chances of collecting these minerals. Here are some known hotspots:

Hawaii: The Big Island is renowned for its olivine deposits, particularly at locations like Green Sand Beach (Papakōlea).
Arizona: The San Carlos Apache Reservation is famous for producing high-quality peridot crystals.
Italy: The island of San Pietro in the Mediterranean is also a historical source of peridot.

Visiting these sites often requires permission or adherence to specific regulations, particularly on Native American lands or protected areas.

Identification and Evaluation: How to Spot Olivine and Peridot

Recognizing olivine and peridot in the field can be both thrilling and challenging. Here are some practical tips for identification:

Color: Look for a characteristic green shade, which can range from pale to intense green.
Transparency: While olivine can be translucent to opaque, gem-quality peridot will generally be transparent with fewer inclusions.
Hardness: With a Mohs hardness of 6.5 to 7, both olivine and peridot can be scratched by quartz, while quartz will not scratch them.

Also, an ideal piece of peridot will have an ‘oil drop’ effect when held under intense light, showcasing clarity.

Collecting and Preserving Your Finds

For rockhounds, collecting olivine and peridot can be a rewarding venture. Here are a few tips for preserving your finds:

Clean with Care: Use mild soap and water to clean your specimens, avoiding abrasives that could scratch their surfaces.
Store Safely: Keep your minerals in padded boxes to prevent damage during transport and storage.
Display Wisely: When showcasing your collection, choose a display that minimizes exposure to sunlight to prevent fading.

Conclusion: The Allure of Olivine and Peridot

The hunt for olivine and peridot is not just about the thrill of discovery but also about connection to the Earth’s volcanic processes. Whether you are a seasoned collector or new to the world of minerals, understanding the significance and formation of these gemstones enhances your appreciation for them. With the right tools, knowledge, and responsible collecting practices, you can uncover the hidden gems that lie within volcanic fields.

Embark on your rockhounding journey today, and you may just find yourself with a stunning piece of geological history in your collection!