About Gemstones

For a mineral to be called a gemstone, it must possess three virtues: beauty, durability and rarity.


The first of the three virtues of a gem is beauty. 

What makes a stone beautiful? Many things. A stone may be beautiful due to its colour, depth of colour, or transparency, or the way it sparkles by reflecting, refracting or dispersing light. Rubies and emeralds, for example, have beautiful transparency and depth of colour. The colour of turquoise is very desirable.And in a good quality diamond, white light is split into spectral colours, creating 'fire'.  colour alone as in the turquoise, or through the splitting up of the white light into the spectral colours, the so-called ‘fire’, which is so well seen as in the diamond. Opals have a beautiful 'play of colour' due to the interference of transmitted light rays. 

A stone's beauty is brought out by the work of the lapidary, who cuts and polishes stones. The amount of facets on a gemstone, and their careful placement, will give a stone more sparkle and enhance its beauty.


Durability is the second virtue. Hardness is one way to determine the durability of a gemstone. This is measured using the Mohs scale, which measures the relative hardness or scratch resistance of various minerals. Diamonds are rated 10 at the top of the Mohs scale, which means it can scratch all other gems on the list. Gemstones in the corundum family (rubies and sapphires) are rated 9, while emeralds are 7.5 - 8. Another measure of durability is stability. For example, an opal contains water, and can crack if dehydrated.


The virtue that is often of greater influence than both the beauty and durability of a gemstone is its rarity. A mineral might be fairly common, but finding very fine pieces of that mineral, suitable for fashioning into gemstones, may be very scarce, as is true in the case of the emerald.  A flawless emerald of fine colour is exceedingly rare and may well command a higher price than a diamond of the same size and quality.

Gemstones at Sargisons

At Sargisons, we select fine natural gemstones. We travel overseas to source unique stones, and stock a wide range of semi-precious stones and fine gemstones. If you are interested in a gemstone of a particular cut and size, we will happily get a range in for you to view, to ensure that you select the stone that's perfect for you.