Kyanite is an one of the more uncommon gemstones set into jewellery, and is found in a variety of colours, most commonly blue, but also occasionally green, grey and orange. Most kyanite you see is quite opaque, with gemmy transparent stones more of a rarity; some top quality blue kyanite is so beautiful it can be mistaken for the finest sapphire, hence its many misnomer names which include water sapphire, sapphire-stone, sapphirete, sapphre, and neelmani or nila-mani (which is actually a Sanskrit word for a blue colour sapphire - I've been told nila means blue, and mani means gem, and is used in parts of South Asia as a reference to sapphire). Please note kyanite is not in any way a sapphire, and is a completely different beautiful gem in its own right.

Kyanite is quite unusual as it possesses two fascinating gemstone characteristics. Firstly, it has what is called a perfect cleavage in two directions, which means it breaks easily along two specific planes (not the more usual one plane). And secondly, kyanite is an example of what is called 'anisotropic hardness'; which means its crystal structure is arranged in such a way that it has varying MOHs hardness along different axes in the one stone; in one direction kyanite is relatively soft (around 4.5 on the MOHS scale), and along the perpendicular direction, it is much harder (up to 7 on the MOHS scale). All this makes for a stone that is quite difficult to cut, and perhaps this is why  this stunning gem isn't set into jewellery more often. 

Kyanite belongs to the same family as andalusite and silimanite. They all have the exact same chemical formula (Al₂SiO₅ ), but because the way they were formed within the Earth was different to each other, their crystal structure isn't the same; andalusite forms in the lowest metamorphic pressure, whilst kyanite in higher pressure (it's also because of these geological variations in formation that you don't generally see these three gems growing together in the environment).

Whilst it doesn't have the same historical or legendary lineage as other more famous gemstones used in jewellery, kyanite is a beautiful collector's gemstone that's perfect for people who are fascinated by nature, the Earth and the processes which make this wonderful planet as it is. Kyanite is an important indicator mineral in certain geological environments and can provide valuable insights into the conditions under which rocks have undergone metamorphism; its presence and distribution are used by geologists to interpret the history of rock formations, which in turn can tell the tale of the wild and exciting history of planet Earth itself.