Antigua and Barbuda contain some of the most amazing stones in the Caribbean.
In this article, you’ll learn more about the geology of Antigua and Barbuda.
Types of Rocks Found on Antigua and Barbuda
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.
The islands of Antigua and Barbuda are volcanic islands that were formed when the limestone on the ocean floor was pushed to the surface by volcanoes that are now extinct.
You can find many examples of limestone as well as a variety of volcanic rocks. You may find examples of carnelian and variscite on the island as well. The island has magnificent examples of karst limestone on the beaches and in the National Parks.
Various types of limestone and volcanic rocks are present on the island that has a long history of stonework.
Limestone is a light colored stone that can easily be scratched with the point of a knife. The stone is formed from the remains of the marine life that thrives in the warm salt water around the islands.
Coral limestone may be formed from the remains of coral reefs that have died around the island. The limestone may contain fossils of shells or skeletons of these animals.
You can identify fossils by seeing inconsistent coloring or texture in the limestone. Limestone that contains a lot of fossils are often porus in appearance.
You can see examples of karst limestone on Barbuda Bay where wind and water have eroded the limestone into beautiful large formations like cliffs.
Pillar Rock is a city in Aruba where there are striking limestone formations and exposed rock faces.
You can also find some very striking karst limestone at the Devil’s Bridge National Park.
You may find a piece of fossilized wood embedded in the volcanic or sedimentary rock found on Antigua and Barbuda.
Petrified wood can be formed when pieces of a tree are submerged under water or volcanic ash which block oxygen. Without oxygen the wood cannot decompose.
The water that surrounds the tree is full of minerals and those minerals fill in the cell walls of the tree and retain the shape and patterns of the original wood.
Volcanic ash carries so many minerals that when it is mixed with the warm sea water it creates good conditions for forming petrified wood.
Much of Antigua and Barbuda is covered in volcanic rock. The rocks are formed when molten lava is cooled after exposure to air or water.
The type of rock that is formed depends on how lava is pushed from the Earth and the composition of the lava.
Dacite is a fine grained rock that is gray to pale brown. The stone is very hard and can be found all over the island.
It is made when very thick lava is pushed to the surface of the Earth slowly as opposed as quickly (as in a volcanic eruption).
Andesite is a very common volcanic rock that is often found in areas of tectonic activity called subdigation.
Andesite is light to dark gray in color and has a very regular texture. Very dark andesite can be difficult to distinguish from basalt.
The stone is created when medium viscosity lava (about the texture of peanut butter) is extruded and cooled quickly by air and water. It contains less than 20% quartz which distinguishes it from other volcanic rocks.
The Andesite on Antigua and Barbuda is mostly created by the melting of the crust.
Basalt is dark in color but fine grained and often has embedded crystals. Basalt is formed from high viscosity lava moving slowly. Flow basalt is generally formed by large lava flows.
Basalt is distinguished from andesite mostly by its darker color.
The name basalt refers to the hardness of the rock. It has been observed by
Tuff is formed from volcanic ash. It is lighter than other types of volcanic rocks for it’s size. Tuff can only be formed following a volcanic eruption.
Rocks that are composed of 75% or more volcanic ash are considered tuff.
The softness of this stone has made it a popular rock for building since ancient times. It has been used in construction of ancient monoliths.
You may observe tuff banding in larger exposed rock faces on Antigua and Barbuda.
This bright blue to green crystal is relatively rare, but has been found on Redonda Island. The crystals for boxlike structures.
These crystals are formed on aluminum containing volcanic rock in the presence of guano.
Variscite is sometimes used as a semiprecious stone in place of turquoise.
A dark red mineral that is usually used in jewelry. These beautiful hard stones have been shaped and formed by the earliest inhabitants of the islands.
The dark red or brown stone can be found all over the island and in local jewelry and souvenirs.
There are examples of carnelian beads as old as the Bronze Age when they were drilled out with bow drills.
The stone was described in ancient Rome, Biblical literature, and in ancient Crete. It was prized for use in signet rings because hot wax does not stick to Carnelian.
Rocks on Antigua and Barbuda
Antigua and Barbuda are great examples of the geology that created the Lesser Antillies. They are a mix of limestone from the sea and volcanic rocks from deep in the Earth.
These geological features should be protected by visitors to the islands. There are some conservation efforts that are unique to these islands.
Use caution when collecting sand or stones from Antigua and Barbuda.
There are ongoing conservation measures to keep the sand on the beaches of Barbuda.
The sand on Barbuda has been collected and sold off the island. It is estimated that over 10 million cubic yards of sand has been taken off the island. This activity has destroyed the vegetation and wildlife that rely on the habitat that sand dunes provide.
There are several National Parks on the islands that have conservation laws:
Devil’s Bridge National Park
Nelson’s Dockyard National Park
Greencastle Hill National Park
Fort Barrington National Park
These are just some of the protected areas on the island where you should be careful about collecting shells, sand or stones.
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