The term Jasper is used here as a catch-all word for different varieties of cryptocrystalline quartz, such as chert, flint, chalcedony and agate. These forms of very fine-grained quartz are very common and occur in a number of different geologic environments. The more complexly patterned and colorful varieties are often associated with, and found within, silicic volcanic rocks. The jasper is formed as a chemical precipitate in fractures and voids in the host volcanics from silicon rich fluids moving through the rock. Changes in colors and patterns are related to variations in fluid flow and minor element variations, such as a change in the amount of iron or magnesium in the precipitating fluid.

​

This jasper is named after the Marston Ranch near Ashwood, Oregon where it was first found. It has been suggested that this deposit is a silicified bog, similar to the Gary Green Jasper and is associated with the volcanic deposits of the Pacific Northwest.

​

Click or tap on image for larger view.