Manos have been typed largely on the basis of the number of faces that exhibit wear, the nature of the worked or worn surfaces, and the general form. Some eight types have been recognized.
=================================================================== | Occurrence by depth (in in.) | |-----------------------------------------------------| Types | 0-6 6-12 12-18 18-24 24-30 30-36 36-42 42-48 48-54 | Total ------|-----------------------------------------------------|------ IA | 28 25 17 10 1 ... ... ... 1 | 82 IB | 12 26 12 8 2 ... ... ... ... | 60 IC | 10 13 10 6 3 ... ... ... ... | 42 IIA | 31 51 19 9 4 2 ... ... ... | 116 IIB | 54 106 76 31 11 2 ... ... ... | 280 IIC | 82 89 68 31 10 3 1 ... ... | 285 IID | 13 15 11 4 2 2 ... ... ... | 47 III | 9 24 16 2 ... ... ... ... ... | 51 ------|-----------------------------------------------------|------ Total | 239 349 229 101 33 9 1 0 1 | 962 | | | Fragments not typable | 1,556 | | ----- | | 2,518 -------------------------------------------------------------------
IA. Natural cobbles with wear on one surface. Cobbles range from symmetrical to irregular in shape: circular to ovoid in outline.
IB. Extended form of type IA, showing excessive wear. Forms all tend toward symmetry.
IC. Elongated "sugar-loaf" in cross section. Entire back surface completely smoothed.
IIA. Natural cobbles with wear on two surfaces. Symmetrical forms range from oblate spheroids to ovoid disks, others are symmetrical. In cross section wear surfaces are parallel to lenticular. Grades into type IIB.
IIB. Same as IIA, but forms are elongated (length always much greater than the breadth).
IIC. Wedge-shaped, ovoid to elongate cobbles. Angle between wear surfaces ranges from 5 degrees to 45 degrees.
IID. Same as type IIC, but one surface is keeled as a result of superimposed wear pattern.
III. Long, narrow, triangular cross section.
Newly acquired mortars are represented but by three fragmentary pieces. Only one is of sufficient size to suggest an outer diameter of approximately 12 inches, and all three appear to be of the cobble type similar to the complete specimen collected in 1947 (Treganza and Malamud 1950, pl. 24, _a_). Considering the area excavated and the very small number of both mortars and pestles that were recovered, it would be safe to assume this complex was of little significance in the history of the Tank Site. Their function was probably concerned primarily with something other than the food economy, such as grinding pigments or functioning in some specific capacity. Wooden mortars and pestles can not be totally excluded, but the great preponderance of manos and metates would probably preclude any serious assumption that mortars and pestles ever played any important roll at the Tank Site.