How Gemstones Acquire Their Colours October 07 2015, 0 Comments

You love to look at precious stones. From canary diamonds to sapphires, your curiosity and taste for exquisite gems lead you to explore the deep, rich colours these jewels contain.

Yet you've always wondered what causes these beautiful talismans to present such vibrant hues and shades. Below, we'll briefly explain the different colours your favourite stones possess, as well as what causes these coloration.

Types of Coloured Gemstones

If you were to look at a wedding ring, a pair of earrings or a gem-ensconced bracelet, you could easily recognise certain common stones. However, not every stone has only one colour. Before you can understand how gems obtain their colours, you should know just how many colours these jewels come in.

Diamonds

Easily recognisable by their transparent crystal appearance, diamonds remain one of the most popular gemstones for many types of jewellery. However, this precious stone comes in a variety of colours, including:

  • Black
  • Blue
  • Brown
  • Green
  • Orange
  • Pink
  • Purple
  • Red
  • Steel grey
  • White
  • Yellow

Emeralds

Unlike diamonds, emeralds only display different shades of one colour. Most commonly, you can identify emeralds by their deep green colour. However, these gems can possess different shades and hues such as:

  • Aqua- or sea-green
  • Blue-green
  • Yellow-green

Sapphires

If you've seen James Cameron's Titanic, then you're probably familiar with sapphires. Renowned for their deep ocean-blue pigment, these stones have become a favourite for accent jewellery, necklaces and earrings. You'll also find sapphires in the following colours:

  • Brown
  • Green
  • Orange
  • Padparadscha (a pinkish orange colour)
  • Pink
  • Yellow

Additionally, these stones will experience a phenomenon called asterism-a highly uncommon feature that gives the stone a star-like imprint visible on the crystal's surface.

Amethysts

Though this gemstone doesn't offer as many colour options as diamonds or sapphires, it does possess different shades of purple and violet. You can find these stones that range in colour from rich, royal purple to light lavender.

Garnets

Many people confuse garnets for rubies. Unlike the ever-red stone, garnets boast a wide variety of colours such as:

  • Black
  • Blood red
  • Brown
  • Colourless
  • Green
  • Orange
  • Pink
  • Purple
  • Yellow

Opals

A native of Australia, this precious stone offers jewel lovers opalescent gems in various colours, including:

  • Colourless
  • White
  • Yellow
  • Black
  • Red
  • Orange
  • Green
  • Blue
  • Brown
  • Rose
  • Slate
  • Magenta
  • Olive
  • Grey

These stones contain a myriad of colours in different combinations. Most common are white and green opals, while the rarest are black opals.

Factors that Contribute to Colour

Now that you know which colours gemstones come in, you can better understand how the following factors work together to create such gorgeous tones.

Light

Gems typically develop in mines and caves. Even though light doesn't strike these crystals frequently in these locations, it still affects a stone's colour. These gems will absorb different wavelengths of light as they form. And since the human eye can only recognise certain light wavelengths, we can only perceive certain colours.

If we can't recognise a certain wavelength that passes through the gem's crystalline frame, it will appear colourless or transparent.

Trace Minerals and Other Elements

In addition to light, other minerals and elements in the earth can impact a gemstone's colour. For example, when a quartz crystal develops over time, small amounts of iron might enter the structure. As a result, the gem will look purple in colour. And the more iron present in the crystal, the deeper the shade becomes.

Other elements and minerals that cause colouring include:

  • Aluminium
  • Aluminium oxide
  • Basalt
  • Beryl
  • Chromium
  • Cobalt
  • Copper
  • Hydrated silica
  • Limonite
  • Manganese
  • Marl
  • Nickel
  • Nitrogen
  • Sandstone
  • Vanadium

The next time you visit your jeweller or talk about the gemstone on your new ring, remember these unique facts about stone colouring. Not only will you impress those around you with your new knowledge, but you'll also understand your gems' true value and history.