Agate recrystallisation: Evidence from samples found in Archaean and Proterozoic host rocks, Western Australia

Driving forces for the weathering and alteration of silica in the regolith: Implications for studies of prehistoric flint tools

“…Once precipitated the silica crystal begins to increase in size, resulting in a decrease in surface defects and a more compact structure (Moxon et al, 2006).…”

“…The variation in crystallinity of quartz, for example, can be evaluated by several methods (Graetsch et al, 1987;Herdianita et al, 2000b;Lee, 2007a;Moxon et al, 2006;Murata and Norman, 1976;Smykatz-Kloss, 1972) including the full width at half-maximum intensity of an X-ray diffraction band, the intensity of peaks in X-ray diffraction patterns (quantitative…”

Cathodoluminescence (CL) features of the Anatolian agates, hydrothermally deposited in different volcanic hosts from Turkey

“…They are widely called under two general names as cryptocrystalline quartz and pseudocrystalline (or paracrystalline) quartz [12,19,7].…”

“…Agates occur in acidic and basic volcanic rocks, and they either form during hydrothermal processes (vein agates) or in sedimentary/diagenetic environments. Each of these types has its own characteristics [12,6,24]. In both cases, because of rapid accumulation and solidification of the silicic acid-rich solutions in different kinds of spaces of host rocks [19,30,27,38], the agates have a cryptocrystalline structure which is formed from microscopic particles, mainly fibrous and partially granular silica particles which are main chalcedonic silica components ( [22,17,18]).…”

Chemical Treatment Effects of Blue, Yellow and Green Colors with Heating Methods on Agates of Cheshme Shoor Area, Qom, Iran

“…Agate relates to silica rock from volcanic origin that is believed to form in the cavities created by vesiculation of volcanic host [2]. Agates have been observed in sedimentary, metamorphic and igneous environments and can be found in every continent.…”