The island of Aruba contains some of the most amazing stones in the Caribbean.
In this article, you’ll learn more about the geology of Aruba.
Types of Rocks on Aruba
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There are two main geological attractions on Aruba; Ayo Rock Formation and Casibari Rock Formation.
These rock formations are big tourist locations and they are a mystery to those who have studied them
Along the North Coast there were once gold mines and the location is not heavily visited by tourists making is still quite remote
Reddish brown in color tonalite is a common rock on Aruba.
It is a fine grained stone that makes up the large rock formation of Ayo.
Tonalite is greater than 20% quartz.
The prehistoric Arawak people carved designs into the rocks that are still visible to visitors
The Ayo rock formation is large and impressive Casibari Boulders.
These enormous boulders are a part of the beauty and mystery of the formation.
The formation stands above the desert and gives a panoramic view of the landscape.
The formation is fairly accessible and has stairs and walking paths around the foundation of the formation.
The boulders are said to resemble birds and animals and it is thought to be a place of spiritual significance.
There is a large formation of igneous intrusive rock that forms most of Aruba.
The roof of the formation is gabbro and Norite.
Gabbro has a speckled appearance and a coarse grained texture.
It was formed by the slow cooling of magma that was pushed towards the surface but was not part of a volcanic eruption.
Gabbro is made of iron and magnesium rich magma, the same type of magma that would form basalt if it was cooled quickly.
Both rocks also contain a fair amount of calcium.
Because of the way it is formed, gabbro can often result in large monolithic deposits.
This large deposit on Aruba shapes the island landscape.
The gabbro on Aruba contains abundant augite.
Quartz diorite can vary in color from
For a long time tonaite was called quartz diorite, but the distinction was made in the quartz composition.
Tonalite contains greater than 20% quarts while Quartz Diorite contains between 5 and 20% quartz.
Prehistoric rock drawings can be seen on the stones.
Aruba was formed by volcanic activity, but because it spent many years underwater during its formation it does contain significant limestone deposits.
Limestone forms from the calcium rich skeletons, exoskeletons and shells from marine life.
As the animals die and the remains are compressed together they form limestone.
Limestone is common in areas with warm water where the necessary marine life thrive.
On Aruba you can expect to see thin layers of limestone and coral debris and karst eroded deposits on the island.
The gold that has been discovered on the island has been found among the limestone deposits.
The fossils of the Ammonoid mollusks are found on Aruba and they are beautiful discoveries for any rock hunter.
The ammonite was named for the mollusk’s spiral shape.
The fossils may be found embedded in clay or limestone deposits on the island.
Ammonite fossils were historically called snakestone because they were believed to be fossilized coiled snakes.
Norite is an intrusive volcanic rock meaning that it was formed by solidifying lava that was not part of an eruption.
They may form large deposits of solid stone.
Norite is a medium grained rock with specked color variations.
Norite is closely related to Gabbo which is a major type of rock found on Aruba.
Norite and gabbo can only be distinguished under a special microscope.
The stone was found in abundance in samples taken by Apollo.
Hypersthene or Ferrosilite
This beautiful smooth stone is very shiny when polished and may be smooth and shiny when you find it embedded in volcanic rock.
It is commonly found in iron meteorites.
Ferrosilite can be gray, brown or green and you can find its smooth deposits inside rougher volcanic rocks.
While it can form crystals, those are very rare.
The stone contains iron and magnesium which distinguishes it from some other types of rocks on Aruba.
The rock has a hardness of 5-6 and its name means “over strength” as it is harder than many similar looking rocks.
Augite is a common mineral found in gabbott which is plentiful on Aruba.
The crystals are usually green, black or brown and they have a translucent appearance.
The cleavage pattern of the rock means that it often breaks at just under 90 degrees.
You can find these stones embedded in the Gabbott that is plentiful all over the island.
It is more common inland than on the beaches.
It may be difficult to observe the cleavage on small deposits and it could require magnification.
Sea glass is a popular target for beachcombing.
The Caribbean islands hold the oldest examples of sea glass.
Sea glass is the result of man made glass and ceramic being disposed of in the ocean and being tumbled in the suft for 10-50 years.
The result is smooth, transparent pieces of glass that appear frosted.
Sea glass can be green, white, brown or ceramic.
Collecting sea glass is a hobby of many, so it can be difficult to find any.
Sea glass is also becoming more rare as humans work to reduce the amount of trash that enters the ocean.
Rocks on Aruba
Aruba is an island formed by magma pushing toward the surface of the earth.
You can discover beautiful stones that were gathered as Aruba rose from the sea.
The rocks on Aruba have indicated gold deposits on the island and Aruba experienced a gold rush in the 19th century.
You can see the sites of the historic mines in three locations on the island.
The mining eventually uncovered 3 million pounds of gold.
Tour the three mines at:
- Arikok National Park
- The Balashi Gold Mill
- Bushiribana Gold Mill
The Arikok National park covers 20% of the island and contains dorite, quartz and limestone as well as examples of cave drawings.
Plan to spend a day at this park and learn more about the island’s geology.
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