John MacCulloch, Explanation of a Supplementary Plate on Vegetable Remains preserved in Chalcedony (1817)
“ Fig. 1. [1] This figure is given for the purpose of explaining the mode in which the fibrous disposition of chlorite is effected. The crystallized arrangement which is here so visible is generally observed in those chlorite fibres which occur in transparent quartz. I I have never observed it in chalcedony, yet there is little doubt that a similar disposition is equally the cause of the fibrous appearance so common in the specimens which have been figured in the former plates, the chief differences consisting in the smaller size and less perfect crystallization of the chlorite scales. ”
