There are currently nearly 5000 minerals known to science, but only a few dozen are common enough to be found widespread throughout the Earth's crust. This article will explain a little bit about some of the most common minerals on the Earth and where the come from.

Inside the Earth

When we talk about the minerals found on the Earth we are talking about those that are found in the Earth's crust, the only part of the Earth really open for us to explore. The crust is a thin layer (up to 100km thick) under which lies the mantle and the upper (liquid) and lower (solid) core.

The Elements

All minerals are made up of a mixture of the 90 naturally occurring elements, and it comes as no surprise that the most common minerals are those that contain the most abundant elements in the Earth's crust.

Table 1. Abundance of elements in the crust

Element Symbol Abundance (%) Oxygen O 46 Silicon Si 27.7 Aluminium Al 8.2 Iron Fe 4.1 Calcium Ca 3.6 Sodium Na 2.8 Potassium K 2.5 Magnesium Mg 2.0 Titanium Ti 0.4 Hydrogen H 0.1 Phosphorous P 0.1 Manganese Mn 0.1

The Minerals

Let's look at some of the most abundant minerals on Earth. Note that the photographs we show are often of exceptionally good crystals and not the form that average specimens of the minerals would appear to be - most rock-forming minerals are simply interlocking grains of a few mm maximum size, these photos show the potential of what these minerals can look like in the rare cases where conditions allow them to grow bigger and more perfect crystals.

The most common mineral in the crust is feldspar according to most references, with up to 52% of the crust being made up of feldspar. But feldspar is actually a group name for several related minerals - so we'll look a little at a couple of examples:













Clay minerals make up 5% (mostly in as ultra-fine particles in sedimentary rocks). After this we have 3% for every other silicate mineral, and only 8% for non-silicates (including carbonates such as calcite and dolomite, oxides such as magnetite and sulfides such as pyrite and pyrrhotite.

Below the crust

The mantle is around 2,900km thick, or about 46% of the Earth's radius, but represents 87% of the total volume of the Earth.

Although the mantle is only 5km below the surface at the crust's thinnest point the challenges in drilling through the crust to reach the mantle are immense (not least because the crust is only this thin in the deepest parts of the ocean.)

But we can deduce a lot about the minerals that make up the mantle from examining fragments of these mantle rocks that are brought up from very deep by volcanoes and from the careful study of seismic data which allows us to understand some of the structure of rocks buried beneath the crust. Computer models can also predict the temperature, pressure and chemistry at various depths in the Earth and from this we can deduce the types of minerals likely to be present.

Here are some of the other major minerals that are thought to make up the mantle:

The Core

We know less about the core than any other part of the Earth not just because it is so remote but because the immense temperature/pressure found there are almost impossible to reproduce in laboratory experiments. We do know that the core is made up primarily of iron and nickel but also containing heavy elements such as gold and platinum in much greater concentrations than the crust. The outer core is liquid, but the inner core is solid. We can't ever take samples of the iron-nickel alloy from the inner core but we do believe the composition to be quite similar to that found in some metallic meteorites.