the process by which silica minerals such as quartz, chalcedony, and opal fill pores or replace existing minerals, rock, or wood.

Silicification occurs in the earth’s interior through the action of hydrothermal (hot) and cold water saturated with silica. As aluminosilicate rock is weathered, a great deal of silica is freed and dissolves. Much of the dissolved silica is carried to the sea, but in places it moves downward and replaces various rock. Hydrothermally silicified carbonate rock is frequently associated with ores of mercury, antimony, and other nonferrous metals. At ordinary temperatures, loose rock on the bottom of lakes and seas is subject to silicification, as is solid rock; this occurs most frequently with limestones and dolomites, more rarely with clays and phosphorites. Accumulations of fine-grained quartz form when carbonate rocks are replaced, and aggregates of quartz and chalcedony develop when clayey rock is replaced. The presence of fine-grained quartz and quartz and chalcedony aggregates in ultrabasic rock indicates that deposits of silicate ores of nickel and cobalt may be found.

References in periodicals archive ?
In this case, the silica saturates limestone layers or creates lenticular forms of silification, and--occasionally--hornstone forms.
Pedogenic silification of sedimentary rocks, such as sandstone and mudstone, during the Early Cretaceous has created the abundant, high quality material available at Quarry 35.
The prospect area is comprised of four hills containing outcropping, low-sulphidation, epithermal Au-/Ag-mineralized systems occurring as veins, breccias, stockworks, and zones of silification along a cumulative strike length of at least 3.
Since silification is the dominant alteration at Meikle, the majority of the ore is competent.
Silification of carbonate pebbles in a fluvial conglomerate by ground water.
Previous results have tended to confirm the existence of a gold-bearing hydrothermal system associated with the argillization and silification of host rocks proximal to feeder structures.
Complex paragenitic relationships among various sulphide minerals and quartz argue for several distinct pulses of mineralization and silification.
Silification zones which host most of the known silver mineralization was intersected in all five holes with visible sulphide mineralization in four holes.
This drill hole intersected the anticipated series of metasedimentary/metavolcanic lithologies with several zones of silification and carbonate alteration.
It is characterized by intense silification and sulphidization and appears to be brecciated.
Three of these intersected zones of, silification, quartz veins, stockworks and sulphide zones similar to the material exploited by the artisans.