12-03. Hematite #1.
Hematite, the rock our ancestor used to draw on cave walls, will be the mineral for week #49.
Hematite is one of the most abundant minerals on Earth – and on Mars too. Apparently, that’s where the planet’s red color comes from. It is a tight, atom packed crystal that has the shape of a hexagon or a scalenohedron – a six-sided polyhedron. It belongs to the trigonal family system and its symmetry is R3c.
It has been used extensively in intaglio engraved gems from Greek and Roman to Victorian times. Renaissance oil canvas painters made great use of it in its powder form because it’s opaque, stable and permanent. Mixed with white it creates a large array of pinkish to light brown colors found in many portraitures of the time.
From a resource by R. Blake, R. Hessevick, T. Zoltai, and L. Finger – a Hematite crystal unit cell from Elba, Italy.