Recently I went back to my old love: grasp a piece of stone, take time to discover it and then just take away bits and pieces... absolutely relaxing after all this figurative struggling, trying, shouting, starting all over again...
A very nice piece of blue alabaster is slowly turning into this strange piece of work - Slowly there is some balance crawling into this thing. Slowly turning blue, slowly sanding and starting all over again and sanding... With some nice music and no machinery for a change. 

hematite found in the sahara desert, Marocco

Just tumbled into minerals... This iron-based mineral hematite' is beautiful:  it can have the shape of a kidney, or a skull.  The Greek word 'aims' means 'blood'. In Dutch we call this stone 'glaskophematiet. 
Large ore bodies of hematite are usually of sedimentary origin; also found in high-grade ore bodies in metamorphic rocks due to contact metasomatism, and occasionally as a sublimate on igneous extrusive rocks ("lavas") as a result ov volcanic activity. It is also found coloring soils red all over the planet...
I have a small specimen in my studio: a present from my parents from when I was about 10 or so... my fascination for rocks and stones goes far back!

http://www.mindat.org/

Malachite is another , green and very common copper mineral, with a widely variable habit. Typically it is found as crystalline aggregates or crusts, banded in appearance. Until the 18th century, the malachite mineral wow used for its green color by painters...
For me it's all about the natural shape! Great stuff! Love it!