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The beryllium deposits at Spor Mountain occur in waterlaid tuff that contains carbonate clasts. Vitric and zeolitic tuffs are present outside the mineralized area whereas argillic and feldspathic tuffs are present within the mineralized area. Early alteration of tuff was characterized by argillization and addition of Si, AI, Fe, Hp, F, Be, Li and many trace elements; advanced alteration was marked by feldspathization, fluorite-silica replacement of carbonate clasts, continued addition of many trace elements, and loss of water. As shown by potassium-feldspar and fluorite abundance, the alteration intensity at the Roadside beryllium deposit decreases with depth but shows a minor increase near the base of the tuff. The beryllium ore body and associated fluorite are near the top of the tuff and are underlain by a thick zone containing lithium-bearing trioctahedral montmorillonoid clay and associated calcite. Beryllium (as bertrandite), lithium, uranium, and other elements are concentrated in fluorite-rich nodules, and magnesium, lithium, and zinc are concentrated in trioctahedral montmorillonoid clay nodules. Most of the nodules are believed to be altered domomite clasts. Manganese oxide minerals occur as nodule coatings and fissure fillings.The elements concentrated at Spor Mountain are tentatively believed to have been derived from a buried granitic pluton by fluorine-rich hydrothermal solutions. These solutions ascended into the overlying tuff where they reacted with carbonate clasts, releasing carbonate ions whose hydrolysis turned the solutions alkaline. Decreasing temperature probably caused precipitation of silica minerals and fluorite, producing and accompanying decrease in fluorine concentration. Increasing pH triggered potassium fixation and resulted in widespread feldspathization of the tuffs. Increasing pH, decreasing temperature, and decreasing fluorine concentration were variously responsible for the breakdown of stable metal fluoride complex ions and for the precipitation of minerals of beryllium, uranium, and other elements.

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