When it comes to buying jewellery, if youre looking to invest in items with precious gems you should understand a little about the stones youre buying, and their differing durability.
When assessing how long a stone is likely to maintain its form, you should measure its general hardness and level of scratch resistance. The hardness of a stone does not necessarily guarantee its durability.
To clarify the hardness of minerals, a German mineralogist developed a scale in 1822 based on ten minerals that are readily available. The scale works by comparing the minerals to each other to highlight the durability of one stone over another. Below weve included the Mohs scale and highlighted where there are variations to the information in the scale.
The Mohs Scale of Mineral Hardness
According to the Mohs scale, diamond is rated at 10 because it is able to scratch all the other gems on the list. Corundum, which includes ruby and sapphire, is ranked nine, topaz eight, quartz seven, orthoclase six, apatite five, fluorite four, calcite three, gypsum two and talc one. The higher the gem is ranked, the more capable it is of scratching and damaging the minerals below it.
The scale does not give all the information needed to make decisions based on gem purchasing though, as the hardness of the stone does not describe its potential fallibility. For example, even though diamond is placed on the scale at 10, it can be broken quickly into pieces, due to its perfect cleavage. This same potential to split under pressure is also true of topaz, which again ranks high on the Mohs scale. There are other gems which dont rank as highly as diamond or topaz, such as Jade (which ranks at 6.5/7 on the Mohs scale), that are incredibly tough as they are resistant to pressure due to their crystal structure.
Other gems can have their stability affected by external factors such as light, heat and chemicals which impact their durability. Aquamarine and peridot will react badly to acid, whereas gems that contain water, such as opal, can become dehydrated and crack if they are left to dry. To decide which gemstone is the most suitable for you to purchase, you can use the information above to consider the factors likely to affect the stone you wear.
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