Kyanite - a mineral under great pressure

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Kyanite - a mineral under great  pressure - tells its story

My Story
Hi I'm the rectangular blue crystal you see in the image and my name is Kyanite.
I am a very useful mineral and form under high pressure deep in the earth.
Where pelitic rocks (like shales and slates) are metamorphosed (buried, cooked and squeezed but NOT melted),  my presence tells geologists the temperature depth and pressure that was needed to form the rock I am originally found in.
I have two friends with the same composition Al2SiO5 we never meet because we are formed under different conditions... kyanite schist (kyanite in blue)

I am quite a useful mineral because I am quite hard and can handle high temperatures.
I'm used in the porcelain of false teeth, to hold the diamond dust together in cutting and grinding wheels and as a rare blue gemstone.