Kyanite is an aluminium silicate with an unusual property - it has a different hardness depending on which direction you scratch it. It is generally blue in colour and occurs as prismatic crystals.
It is found in aluminium-rich regional metamorphic rocks such as mica-schists and gneisses. In Australia, the best-known locations where it can be found are in the Harts Ranges in the Northern Territory (where the one pictured is from) and from near Broken Hill in New South Wales. It can also be found in a number of other locations in Australia and New Zealand.