Crystals, Rocks, Minerals, What Exactly Are They?

What exactly is a crystal, rock and a mineral?  This is something that many people struggle to answer when asked and I hope this article makes things a little clearer.  As someone who has no specific qualifications in this field but who is genuinely passionate about it, I have tried to keep this article interesting and have written it in a way which I hope you’ll find easy to understand.

During a recent trip to London’s Natural History Museum, I spent almost three hours looking at crystals, rocks and minerals and would have gladly spent another three hours doing so had it not been for the fact that my companion found the exhibits exceptionally boring. Whilst I fully appreciate that rocks and minerals may not be the most exciting objects to look at in a museum, for me they’re the main attraction.  People love looking at sparkly gems and diamonds and wherever they’re displayed you’ll find hoards of people but minerals on the other hand, can for some be visually uninteresting and their primary purpose is to demonstrate the Earth’s mineral-forming processes and the varying arrangements of atoms which is why the mineralogy section of a museum is almost always empty.

Despite not being overly popular, crystals, rocks and minerals are the building blocks of our planet and they’ve been collected, used and enjoyed by humans since the dawn of time. During my travels around the world in search of rough and polished minerals to buy for my business, Stone Mania, I always take a day out to visit a museum and have over the last twenty years or so, seen some truly magnificent collections.  Although we’re surrounded by rocks and minerals in one form or another almost every day of our lives, trying to explain exactly what they are is no easy task.

The study of crystals is known as crystallography, the study of rocks is petrology, minerals is mineralogy and gems is gemmology. Geology is the study of the Earth, its history, the rocks of which it’s constructed, their structure, where they came from, how they have changed over time and how they continue to change.  These subject matters are all related to science and the one thing they all have in common, is crystals, rocks and minerals but what exactly are these strange inanimate objects?

Minerals are made up of naturally occurring solids which are inorganic meaning they do not contain any living matter.  To be correctly classified as a mineral it must also be crystalline which means it contains a microscopic and well ordered arrangement of atoms that form a repeating three dimensional crystal lattice which makes up a solid body known and that’s known as a crystal. The specific arrangement of atoms is known as the crystal structure and the process of crystal formation and its subsequent growth, is called crystallization.  Crystals can be large enough to be seen with the naked eye or so minute that they can only be seen through a powerful microscope but irrespective of size, they all have one thing in common which is they’re all made up of a symmetrical, three-dimensional arrangements of atoms.  Crystals are classified according to their individual crystal structure because the manner in which atoms are arranged in a crystal, is not always the same.

Some minerals have the ability to crystallize in more than one way and the result of a different crystal structure will be a different mineral.  For example pyrite and marcasite are both identical in that they’re iron sulphide (iron and sulphur) minerals but the one you end up with totally depends on which crystal structure is present.

When a mineral-like substance is not crystalline (lacking crystal structure), it’s more correctly known as a mineraloid and examples include amber, jet (a very compact form of coal), shungite, opal and pearl to name just a few.

Most minerals are chemical compounds which means they’re made up of two or more chemical elements.  A chemical element is a substance which contains just one type of atom, if more than one is present it’s known as a compound. An element can either be a solid, a liquid or gas.  Although most minerals contain two or more chemical elements some such as copper, sulfur, gold and silver occur as a single element meaning they only have one type of atom.

The exact number of minerals which are known varies from 2,722 to 6,500 depending on the reference that you read.  Some of the most common which are found in rocks at the Earth’s surface include quartz, feldspar, mica and olivine.

Rocks can be made up of either a single mineral or a variety of different ones and unlike minerals, they do not have a fixed composition or an ordered arrangement of atoms (crystal structure). Certain minerals and groups of minerals are present in some rocks in greater abundance than in others and a few contain no minerals at all. Coal is classified as a rock yet it’s made up purely of decayed vegetation. Rocks are classified into three different groups, igneous, sedimentary and metamorphic and together they form the building blocks for our planet.

Igneous rocks are formed when molten rock or magma solidifies and they’re either classified as extrusive or intrusive depending on whether the magma had emerged onto the Earth’s surface or not before crystallizing.  Magma and lava is exactly the same the only difference being magma is molten rock beneath the Earth’s surface and once it’s been spewed out by a volcano, it becomes known as lava.

Basalt and granite are both igneous rocks, basalt makes up the vast majority of the ocean floor and is produced through the eruption of underwater volcanoes, granite is formed by magma which solidifies deep underground and makes up the majority of the continental crust which is the layer of rock that forms the continents. Some granite in Australia is believed to be four billion years old however rocks of this age are difficult to date accurately because of the extent that they’ve been altered by the environment. Obsidian is also an igneous rock which is natural volcanic glass and forms when lava solidifies so rapidly that crystals do not have a chance to grow hence it’s not crystalline (no crystal structure present) so is correctly identified as a mineraloid.

Metamorphic rocks are formed when intense heat and pressure changes the composition and arrangement of minerals within an existing rock and the process may also change its appearance and texture. Metamorphic rocks do not melt, they undergo a physical change due to extreme heat and pressure. Rocks that melt go on to form igneous rocks.  Garnet is a mineral that’s produced through the metamorphism of basalt and marble is produced through the metamorphism of sandstone which is a sedimentary rock.

Once rocks and minerals are exposed to the Earth’s surface they begin to weather and erode and in doing so, they break down leaving nothing more than sediments.  Over time these sediments are carried mainly by water and as they’re redistributed, a process known as cementation takes place and over time, sedimentary rocks begin to form.  The structure of a sedimentary rock is usually layered and will often include fossils which are the remains of marine plants and animals. Some of the best known sedimentary rocks include sandstone, rock salt, clay and limestone.

So in brief, crystals are made up of repeating groups of atoms and are the basis for minerals, minerals make up rocks which are grouped into three main types and rocks are the building blocks of the incredible planet that we live on.

To view our collection of crystals, rocks and minerals, why not drop by and have a browse through our website, Stone Mania.


About Stone Mania - Crystals, Rocks, Minerals
Stone Mania is a London based wholesale and retail supplier of crystals, rocks, minerals and ladies gemstone pendants. We are a small team of mineral enthusiasts who travel to Africa, Asia and the USA several times a year in order to buy pieces for our collection. As well as shipping minerals back to the UK, we also bring up to seventy kilos back with us at any one time and thanks to our wonderful clearing agent and UK customs, we're usually through in pretty good time. Stone Mania started life in the winter of 2002 and those early days were spent trading one day a week from behind the counter of a cramped stall in Camden market. Dedication, passion and a huge amount of hard work meant that the business grew steadily and went from strength to strength and despite a few ups and downs especially during the credit crunch of 2008, we never had any doubt that Stone Mania would pull through. Fifteen years on and we're just as enthusiastic about Stone Mania as we were on that very first trading day back in 2002. We love what we do and are very happy to say that our customers also love what we do and together, we all get to enjoy some of the worlds most beautiful and fascinating crystals, rocks and minerals. If you're a retail customer you can shop online with us through our website but for those interested in buying wholesale from Stone Mania, please contact us first in order to set up an account.

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