Variations in zircon crop measurements due to weathering of igneous rocks

Zircon is one of the most widespread heavy accessory minerals in all rock types of all ages. Recent investigators have used statistical parameters of zircon crystal measurements to draw a variety of petrologic conclusions. Experiments have shown that igneous rocks from the same outcrop liberate similar zircon crops. Length and breadth measurements were made for 13 paired samples. Each paired set consisted of a fresh rock and an altered rock from the same exposure. The altered rocks liberate a zircon crop which is more numerous, larger in maximum size, mean size, and size range, and have larger elongation ratios. The absence of longer crystals in the fresh sample is due to breakage during grinding. Future investigations drawing conclusions and correlations from such measurements must take this source of error into consideration.