Yes, you are correct on the heat treated statement for sure, as a majority of the ones I have found are made of poorer quality chert that was better utilized for the knapping process by heat treatment. That being said, if the maker had higher quality material, coastal plains chert for example the heat treatment process may have not been utilized. I am unfamiliar with the black chert of rocks piece, but what some see as a cortex of brown on the stem I see as the possibility of costal plains chert? Another oddity I have found on water submerged village sites where the color of materials used, and the process of tool making can be found. Is that often they have hauled in an outcropping of particularly type and outward material rocks, maybe found close to camp since some of these rocks are over basketball size. It is amazing to see how many times the color and quality will change the closer to the core. For example I have found rice grain chert started performs with part of the core apparently agitized. And then a identical outward appearance rock that once they got to the usable core and attempted to use it, they discarded due to poor quality.
