by Louise Schoneveld

Out of “the big 4” gemstones, we’ve already learnt about the two corundums; ruby and sapphire, now it’s time to go green with emerald.

Cut gemstones of Emerald Image from -
Cut gemstones of Emerald Image from –

Emeralds are a variation of the mineral beryl with the formula Be3Al2(SiO3)6. Pure beryl is colourless however trace amount of elements can cause beautiful colourations. Fe2+ within a beryl can make an aquamarine gemstone (fig 2.) while Fe3+ causes a golden variation known as “golden beryl” or “Heliodor” (fig 3.). The classic green colouration of emeralds are given by inclusions of chromium and occasionally vanadium.
Fig 2. Aquamarine variation of Beryl. Image from
Fig 3. Heliodor gem Image from
Hardness and crystal habit:

On the Mohs scale of hardness emerald ranks a 7.5-8, which is harder than quartz, and equal with Topaz. Beryl usually grown as prismatic hexagonal crystals and can be striated lengthwise as displayed in fig 2.

Cheeky gemstone tricks:

As only the deep green beryl has a high value as an emerald, the light green variations are often heat treated to produce more valuable aquamarines. These gems are usually heated at between 400-450 C to ensure a beautiful blue. [1] This is much lower than the heat treatment required to improve sapphires.


Good quality emeralds range from US$7,500-$15,00 per carat

Good quality aquamarine are roughly US$200 per carat

Good quality beryls range from range from US$33 for colourless to US$171 for light green coloured per carat.

Where to find:

Sadly, you cannot find emeralds in Australia, not even in Emerald, QLD. The largest producers of emeralds are Colombia (80%) and Zambia.

The more you know about the gems you buy, the most interesting they are…