Brown Tuff

Most commonly, zeolites are found in series of sedimentary rocks which contain pyroclastic material and are formed during the devitrification of this material. If the rocks are silica-rich, the zeolite species formed seems dependent upon the bulk composition and burial depth or temperature of formation (Hay, 1966). They are most frequently accompanied by silica in an amorphous or cryptocrystalline form (opal, chalcedony). Analcite and all other compositional intermediates up to the silica-rich clinoptilolite are found in this association. The most comifton clay mineral in such tuffs is montmorillonite. Zeolites are sometimes found with glauconite (Brown, et al . 1969) or celadonite (Hay, 1966 Iijima, 1970 Read and Eisenbacher, 1974) in pelitic layers or acidic eruptive rocks... 

Luhr JF, Giannetti B (1987) The Brown Leucitic Tuff of Roccamonfina Volcano (Roman Region, Italy). Contrib Mineral Petrol 95 420-436 Lustrino M (2000) Volcanic activity during the Neogene to Present evolution of the western Mediterranean area a review. Ofioliti 25 87-101 Lustrino M, Dallai L (2003) On the origin of EMI end-member. Neues Jahrb Mineral Abh 179 85-100... 

Bonatti and Galitelli (1950) dark brown clay occurring as patches and veins in a diatomite bed overlain by volcanic tuff, evidently formed by percolating ground water, Bagnoregia, Italy. 

The type section of the Edlin Formation, which is laterally equivalent to parts of the Spurs Formation, is located 1 km north of Mt. Glasgow. The Edlin Formation is composed of fine-grained sandstone and mudstone containing lenticular bodies of oosparite limestone up to 5 m thick and less than 50 m long. It also contains tuff beds, conglomerate, and reddish-brown mudstones which contain probable mudcracks, indicating that the redbed sediment may have been exposed at the surface (Laird and Bradshaw 1983). 

S.28.12.63) Vitric-crystal tuff ( ) containing quartz and plagioclase phenocrysts in an aphanitic groundmass. Red-Brown Member, Bragg Valley. 

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