automatic point counter
An electronic control panel designed to count the number of times a particular mineral
is recorded on multiple, closely spaced traverses of a thin section
viewed down a polarizing microscope
. The control panel, which contains a bank of recording buttons, each assigned by the user to a particular mineral, is linked to a thin-section holder mounted on to the stage
of a polarizing microscope. The holder is designed to move the thin section by a predetermined distance (variable from 0.001 to 1 mm) in one direction, after the user has pressed the control panel button assigned to the particular mineral observed under the eyepiece cross-wires
. At the end of a complete traverse, the holder automatically resets by a predetermined distance to start the next traverse. On completion of all the traverses, the control panel shows the number of times each mineral was recorded and can recalculate this as a percentage of the total number of points. This gives the percentage volume of each mineral recorded in the rock.