Give a rock name for sample. Note that the colour of this type of rock varies greatly, depending on the abundance of organic matter and iron oxides. Samples are both carbonate rocks. Describe their textures.
Sample is a limestone. How did it form? Sample 39 is a dolomite and can be distinguished from sample 40 in that it does not react in dilute HCl (it would react slowly with stronger HCl). Its darker colour results from a greater abundance of organic matter.