Stonecutter mainly, as well as others, should be abe to recognize some of the raw gemstone materials illustrated here.
working from the left jade, aquarmarine, amytheist or a topaz, bottom left either garnet or ruby, saphire and citrine in the middle right with and emerald in the middle of course(being my birthstone)…thought about the saphires on the right side but didnt know for sure…I wokeup at the key board this morning …and my legs are numb and my eyes are still focusing and my back is killin me…note to self…dont do that anymore…
nice colors. it looks in depth and the stokes really look impresionistic (<- is that right ?) peace of art
You give me too much credit, DeeVee! 
My training by the Gemological Institute Of America taught me that there are over 120 transparent to transucent materials capable of being facetted, and tourmaline for instance, (One material), comes in a huge range of colours, including black!! 
(And sapphire comes in blues, oranges, yellows, greens, and reds…Which are then called Rubies, the red forms of corundum, which is the mineralogical name of the material)
That being said, this is really nice…It is your brushstrokes I think that I find most interesting, and if you don’t have a tablet yet, I don’t have a clue why not! If ever somebody could take full advantage of one it’s you! 
im not really good at finding colors from materials in rocks however stonecutter is the person to listen to sinces this is his obsession…
Thanks SC. I began taking a course from the GIA, Paid for it and asked them to send me all the matterial, but never actually sent any lessons back to them, it was on Manufacturing and Jewelry design. There are a lot of recognizable stones in this image.
Regarding a tablet, I have been trying for a while to obtain a tablet, but have refrained from ordering one, as I intend to pick one up when next I visit the States. SC you have perked my curiosity, what is so different about my brush strokes ? I thought everyone who uses ZBrush use the same brushes. just joking.
Hey DeeVee, even though you are joking, I’m going to respond anyway!
The difference in the way you use brushes, in my opinion, is based on your aversion to modelling, combined with your previous experience in standard ‘Coloured-goo’ painting. I think this leads you to a place where you paint as if the computer wasn’t there…In other words, you see the transparency of the interface, and work as if on canvas, rather than with glowing dots of light…
By the way, you definitely capture carribean water, as a general observation on your other works… 