Colour Variation in Granite

In this guide, we will seek to explore the fundamental causes of colour variation in Granite. Each colour has it’s own origins, and with it, is exposed to a number of unique variables which can affect how an overall piece can appear, and differ from smaller samples which may have been seen.

Granite is the most volatile surface material in terms of colour variation. To understand why, it’s important to consider where granite comes from and what this means for its’ overall appearance.

Mineral composition

Granite is comprised of several key mineral groups, in varying quantities. Feldspar, Quartz, Micas and Amphiboles. As can be seen on the illustration below, the ratios between these mineral groups can vary wildly while still falling within the broad definition of Granite. To get an idea of just how randomly granite can form, even within the feldspar category of minerals, colours can include white, pink, grey, brown, yellow, orange, red, black, blue or green, and can vary in translucency.

Composition of Granite

source: Geology.com

Particular quarries will be the home to a particular blend of minerals, ensuring a degree of similarity between worktops of that range (such as Silver Paradiso, or Thunder White). Even within these variants, we at Sheridan grade and colour match our Granites on arrival, to categorise these as specific batches. This ensures we can still quality control and deliver colour matched worktops (to the extent to which is possible) despite the random nature of Granite.

Impact on Colour

Granite is formed when minerals are exposed to intense heat and pressure beneath the earth’s surface. Typically, the darker the Granite, the more heat pressure it has been subjected to, and the denser it is as a result. Because this is far from a controlled process, the results can vary significantly. Some good points to consider are:-

  • Colouration – Lighter colours in particular may change over time as a quarry is exhausted.
  • Crystal density – Crystals may become more or less frequent and/or fragmented.
  • Presence of dark or light patches – these ‘mineral streaks’ may not be obvious on smaller samples
  • Colour spots – Light variants in particular may have coloured spots, which can alter in colour, size and frequency.
  • Veining – veins can vary in width, hue, length, frequency and direction.

    A good rule of thumb is to consider darker, more repetitive colours as more stable, while lighter, veined colours have more potential for variance. While lighter colours can be unpredictable, the unique and untamed styles they deliver is the reason why people love Granite as a material.