Types of Rocks on the Virgin Islands (British and US): Guide to the 7 Most Common You’ll See

The Virgin Islands are volcanic islands that have a lot of interesting rocks

St. John, St. Croix, St. Thomas are the main islands that make up the Virgin Islands and they each have their own geology, but the islands have the same volcanic origin.

Types of Rocks on the Virgin Islands

Disclaimer

The information provided in this article by YesDirt.com is for informational purposes and is subject to change. Laws are updated. Accessibility guidelines and restrictions change. Be sure to confirm the land status and collection rules before you travel to an unfamiliar location or collect any material.

Molybdenite

More common on the British Virgin islands. Molybdenite is a very smooth stone that feels a lot like graphite. It can be found on Virgin Gorda Island.

It is made of sulfur and molybdenum which gives it a very smooth feel and metallic look. It breaks easily into thin layers and has an even cleavage.

Molybdenite is black, dark gray or gray and very soft to the touch. It marks on paper like graphite.

Molybdenite can only be differentiated from graphite with special equipment. It can also be tested with acid solutions as graphite does not dissolve in acid, but molybdenite does.

It is formed in areas where the rock formations have been formed in hot water. These formations on Virgin Gorda Island likely were formed when the island was still being formed under the water’s surface.

The mineral forms stunning hexagonal crystals embedded in other sulfur containing rocks.

Sulfur

The Virgin Islands are rich in sulfur and you can find examples of crystalized sulfur.

Sulfur crystals can be incredibly beautiful and usually present in a bright yellow, but can be orange, white or light yellow.

Sulfur was known as brimstone for many years as it was associated with the lava flows where it is often found. It often forms as a result of the gaseous form of sulfur crystallization as volcanic gasses settle and cool.

Sulfur crystals are most commonly found in sedimentary rocks and it forms very square dipyramids.

Sulfur crystals are often found as a yellow coating on other stones, these crystals are very small, but take the same color and shape.

Quartz

Quartz highly recognizable hexagonal crystals may be found along the coast of St. Thomas, St. Croix, Virgin Gorda and St. John.

The quartz found on the Virgin Islands is generally white or colorless, although other color varieties are possible.

Quartz is one of the oldest recognized rocks. It was identified in ancient times as kristallos.

Made up of silicon and oxygen, quartz most often forms trigonal crystals that are vulnerable to microfracturing when heated.

There are significant differences between quartz formed below 573 degrees and those formed above, so if quartz passes above 573, it may expand and fracture.

The temperature also determines the crystal structure. The high temperature quartz is what forms the desired hexagonal crystals.

Quartz is the second most common rock on earth and forms beautiful crystals that are worth collecting.

Prehnite

Prehnite is a bright green rock that forms in globular formations, it looks like bright green gumdrops.

Prehnite has a pearl-like luster and can be very brittle.

Samples of gem quality prehnite have been found on St. John in small quantities.

Prehnite crystals are often found as deposits within the basalt formations that are present in the Virgin Islands. These can appear as bright green spots on a darker rock.

The prehnite crystals will have a smoother feel and that pearl luster.

It is mined throughout the world, and gem quality deposits are found in basalt formations like those on the Virgin Islands.

While it can also be found in white, tan, gray or colorless variations, but green is the most common color.

Prehnite is fairly rare and the deposits are often depleted quickly after they are discovered.

The crystal is believed to represent unconditional love.

Keratophyre

This rock is a volcanic rock that forms strands that appear similar to wood grain. It is formed by lava flows that cool slowly.

It is similar to traychite, but contains more sodium.

Keratophyre is found in Limestone Bay on St. John mixed with basalt.

Leucoxene

Small granular brown to yellow stones may be leucoxene. These small shiny stones are related to titanium, rutile and anatase.

Leucoxene can be used in cosmetic and paint pigments or in the processing of titanium for aircraft.

Leucoxene refers to the small size of the particles. The particles themselves are most commonly made up of rutile.

Rutile is a titanium oxide and a source of titanium. It can often have a red luster and it has a very high light refracting indices.

The light bending properties of rutile means that the leucoxene is also used in the manufacture of some optics.

Limestone

Limestone is a common rock found in the Caribbean, but in the Louisenhoj Formation on the Virgin Island of St. John there is a rare type of limestone.

The limestone found here is intermixed with volcanic rock. There are layers of augite andesite, breccia, basalt and limestone.

You can visit Limestone Bay to see the limestone formations and you can swim out to the coral reef. The beach is not very populated, but has some strong currents right off the beach, so be careful when visiting this beach.

Collecting Rocks on the Virgin Islands

The Virgin Islands are owned by the US and British Government, so the laws are different on the islands, but the principles of conservation are the same.

We want to protect the natural beauty of the Virgin Islands for future generations. Please consider purchasing ethically collected samples from local sources.

Never collect samples in National Parks, which are protected areas.

Be sure to obey all posted signs and local laws when collecting rock, sand or shell pieces on any beach or tourist locations.

When traveling across borders be sure to declare any rocks, shells or sand you are bringing with you.

Rocks on the Virgin Islands (US and British)

The Virgin Islands have a volcanic history which creates some beautiful quartz, basalt, limestone and other mineral deposits.

Visiting the large National Park on St. John is a great location to see the diverse geology of the islands. The Virgin Island National Park is full of historical sites, coral reefs and sponges and plant and animal species.

The volcanic rocks and calcium rich warm water that surround the island have created beautiful and interesting formations.