As arguably the most popular stone material used to make memorials it’s common for people to ask themselves “how does granite get its colour?”.
One thing that leaves many memorial buyers perplexed as well as amazed is the fact that granite memorials are available in a wide range of colours, shades and patterns.
This is one of the main attributes that makes premium granite such a popular stone material of choice for memorials, alongside its durability, strength and fair affordability.
What gives granite its colour?
And…
Why does granite come in so many different colours?
These are the questions that memorial mason customers often ask as they admire the striking beauty of granite while browsing headstones and other memorials in a showroom.
What is Granite & How is it Made?
Stone granite is classed as an intrusive igneous rock that’s composed of various minerals, many of which can be easily viewed by the naked eye.
For the record, being an igneous rock means granite is derived, or solidified, from molten rock.
Molten rock containing a high content of silica, minerals, and alkali metal oxides seeps into gaps in sedimentary rock layers before slowly cooling and solidifying underground over the course of millions of years, creating the granite we know, love and widely use for many different things – including headstones and memorials – throughout the world.
As the molten rock gradually cools over time, crystals form at different periods of time from the various minerals that are present which alters the final appearance of the granite.
One piece of granite typically consists of 20-60 percent quartz, 10-65 percent feldspar, 5-15 percent mica, and minor or trace amounts of amphiboles and other minerals.
If the rock doesn’t contain at least 20 percent quartz, then it isn’t considered granite.
Fun Fact: The granite rocks found on earth today began forming during the early geologic periods, some as early as the Precambrian age (which started about 4.5 billion years ago), making them the oldest rocks on the planet. Furthermore, the Precambrian period preceded the Cambrian period, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied.
What Gives Granite its Colour?
The colour of granite is determined by the variety and ratio of minerals within its make-up.
This is because minerals absorb different amounts of light wavelengths, which in turn gives each mineral a different colour – so, depending on which minerals are predominant within the rock, the colour and hue of that particular granite will sway towards the colour make-up of those minerals.
The 20-60 percent quartz is typically milky white or colourless, and the other minerals that are present then add the colouring or hue to it – this is why granite colours and patterns are so unique.
We will soon go into the mineral breakdown that determines each granite colour, but to give you a quick example – if magma cools and solidifies with a higher percentage of potassium feldspar compared to other minerals that are present, then chances are it will form a pink granite.
Black with white speckles is the most widely used granite colour, and this would mean that the magma solidified with a high percentage of quartz and amphibole.
It’s all very scientific and if this is something that interests you then you may want to look into the study of mineralogy.
The Colours of Minerals in Granite
Below is a list outlining the primary colour of common minerals so that we can understand what colour the granite is likely to be if a high ratio of that mineral is present.
With that said, do bear in mind that many of these minerals can be found within some or even all granite colours, so the overriding colour comes down to the combination and ratio of each mineral that is present within the rock.
- Quartz: Milky White or Colourless
- Feldspar: Off-White
- Potassium Feldspar: Light Pink to Red
- Biotite: Black or Dark Brown
- Muscovite: Light Gold or Light Yellow
- Blue Labradorite: Blue
- Amphibole: Black or Dark Green
If you come across a memorial that looks like it was made from granite in a pure solid colour with no visible grains or pattern, the chances are it is either some other igneous stone or was created using a man-made material like quartzite, which is made to mirror the appearance of granite.
What Makes Granite Black?
Black granite gets its colour and glassy appearance when it’s made up of around 20 percent quartz along with various other minerals, like biotite and/or black mica.
The various other minerals that are present can also leave the black granite with different coloured hues.
For example, it’s common to see a black granite headstone with a brown, yellow, red, or other hue coloured finish.
Many black granites also contain small white specks which are crystal specks of feldspar.
What Makes Granite White?
White granite contains a high percentage of quartz and feldspar, which gives it a milky off-white and somewhat opaque appearance.
Many white granite memorials also contain black spots of different sizes which is likely due to the presence of small amphibole grains.
What Makes Granite Black & White?
Some granite has an equal blend of both black and white, and though this isn’t as commonly used in the specific creation of memorials, the colour combination is due to an equal amount of quartz, feldspar and amphibole.
What Makes Granite Grey?
Grey granite gets its colour from a high ratio of colourless quartz that reflects the other various dark and light-coloured minerals surrounding it.
What Makes Granite Pink?
Pink granite gets its salmon tone from a high percentage of the potassium feldspar mineral.
Within the material of pink granite, you can often see small specks of semi-transparent milky quartz, dark specks of amphibole, and opaque white feldspar.
What Makes Granite Red?
Red granite is rich in potassium feldspar, just like pink granite, only with red granite the feldspar produces a colour that’s more akin to a shade of red rather than pink.
It also often appears as a more orangey red.
Iron oxide is also present in hematite grains within the feldspar, and this can also add a red hue to the colour of the granite.
What Makes Granite Yellow?
Yellow granite gets its yellow or goldish colouring from muscovite, which is a member of the mica mineral group.
Some granites have just a hint of a light-yellow hue, while others are a deeper shade of yellow, or appear as more of a beige hue or even gold.
What Makes Granite Brown?
Brown granite gets its colouring from the presence of biotite minerals within the mica group.
Many brown granite memorials often have a red hue due to a blend of pinkish-brown feldspar crystals.
What Makes Granite Blue?
Blue granite receives its blue colouring from a high concentration of sodalite within the rock.
Sodalite is a blue coloured mineral that mainly consists of aluminosilicate and chloride of sodium.
Other blue coloured igneous rocks, such as larvikite or anorthosite, are also often referred to as a type of “blue granite”, although they are not actually granite rocks.
What Makes Granite Green?
Green granite can get its colour from amazonite, also known as amazonstone, which is a variety of potassium feldspar.
Granite that contains a lot of amphibole can also result in a dark green colour.
Like many blue granites, green granites are often referred to as “green granite” even though it is often not granite. It is often a green soapstone that’s marketed as green granite, or a variation of marble containing serpentine, as actual green granite is rare.
