Types of Rocks found in Montserrat: A Guide to the 7 Most Common You’ll Spot

Montserrat contains some of the most amazing stones in the Caribbean.

In this article, you’ll learn more about the geology of Montserrat.

Types of Rocks found in Montserrat


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.

Montserrat is a small island that was formed by a group of smaller volcanos. The volcano found on Soufriere Hills in Montserrat is one of the most studied volcanoes on Earth. 

The lush island of Montserrat is sometimes called the Emerald Island of the Caribbean because of its rich vegetation and its connection to Ireland. The island was settled by many Irish settlers in the 1600s. 

Half of Montserrat is an exclusion zone after volcanic activity in 1995 which destroyed the capital city of Plymouth.

The island is divided into several zones with various restrictions on entering the area due to volcanic activity. 


Basalt is the name for hardened lava that has cooled quickly after being exposed to air or water.

Basalt can range in color from light gray to dark gray and has a fine texture. 

Basalt is plentiful in many Caribbean islands, but on Montserrat only a small percentage of the rocks are Basalt. 

The vegetation on Montserrat is much more rich than most islands in the Lesser Antilles. The rich soil is created by the decomposition of limestone which is much more plentiful on the island. 


Olivine is a great find for its brilliant green color. It can range in color from dark emerald, to pale yellow or in the presence of iron can become reddish. 

Olivine forms orthorhombic crystals which often form squareish or boxy crystals. 

On Montserrat you can find olivine embedded in the local adesite on the beaches close to Shoe Rock, Centre Hill  and in many locations around the Soufriere volcanic area.  

These crystals may be very small and difficult to see embedded in the dark andesite. 


Another green crystal that you may find on Montserrat is Pyroxene. Pyroxene is dark green in color and forms single chain crystal formation resulting in long square crystals. 

Samples of bandaite and hornblende containing pyroxene crystals have been found all over the island. 

Pyroxene has also been found in a meteor from Mars. 


Hornblende is a general term that is used to refer to silicate minerals that form needlelike crystals. 

The minerals in the Hornblende family are light green to dark black but transparent. Hornblende is generally found in the presence of other volcanic rocks like basalt and andesite. 

Hornblende is often called basaltic hornblende as it is only ever found in conjunction with other volcanic rocks. 


Andesite is a volcanic rock that is formed during a volcanic eruption as the rock cools. 

Andesite is found all over the island as a result of recent and historic volcanic activity. This fine grained dark colored stone is often embedded with other crystals. 

You may find Andestire with small green olivine crystals embedded into the stone or clear quartz crystals. These crystals may be too small to be seen with the eye, but there are stones with larger crystals embedded. 

The difference between basalt and andesite is that andesite contains less silica. This means that it forms from a lower viscosity lava flow. 

The interesting thing about the volcano on Montserrat is that it has multiple lava domes that contain different types of lava that have created different types of rocks to be found on the island.  

White Pumice  

White pumice is a volcanic rock that is formed during a volcanic eruption when the highly pressurized rock quickly expands. 

White pumice is an extremely porous stone that is very light for its size. Some pumice can contain crystals of other minerals. 

On Montserrat white pumice can be found at the base of St. George Hill. 


Sulfur crystals are present on Montserrat in the area surrounding the Sufriere volcano. 

Sufriere is a word derived from French meaning “sulfur in the air” and as a result there are several volcanoes with the same name. 

The volcano has thrown out a lot of sulfur and some of the sulfur has crystallized into bright yellow crystals that can be found around the volcanic area of the island. 

These crystals are often embedded into a matrix of other stones. 

You may also see bright yellow or green sulfur crystals forming in caves or areas of water run off where the rain water has leached the sulfur out of the stones and formed stalactites. 

Sulfur crystals are often found in hot springs and wet areas as it is a highly soluble mineral.  

Volcanic Activity and Exclusion Zone

In 1995 a volcano in Soufriere Hills erupted killing 19 and destroying the capital city of Plymouth. This eruption destroyed the airport and much of the housing on the island. 

As a result of the eruption half of the population have left the island. The volcano is especially active as it is composed of several lava domes. 

To this day, two thirds of the island is now an exclusion zone. The exclusion zone is divided into different areas of restricted access to citizens and casual visitors.

The volcano was still active, in 2013 the volcano erupted again and there continue to be ash and steam events.  

It is possible to visit this active geological site with a government tour guide. You can find the recommended tour guides on the Montserrat Tourism Website

Rocks on Montserrat

Montserrat is an incredible destination for geology enthusiasts as most of the rocks found on the island have volcanic origins and the volcano responsible is still very much alive!

The volcano is the most studied volcano on Earth. 

Scientists believe that the behavior of this volcano has not changed too much over time and they hope that studying the volcano will give insight into the activity of other volcanoes.

If you visit Montserrat, plan to schedule a trip to the exclusion zone with a guide to see the buried city of Plymouth that lies very much in the same state as it was directly after the eruption in 1995, 2001 and 2013 among others.  

Be sure to only collect rocks where you are permitted to do so and be sure to declare any rocks to customs officials when traveling internationally. 

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Types of Rocks found in Montserrat