TECHNOLOGY FOCUS - BIOLOGY - Preferred Plant: The method (M1) uses a plant material that is selected from at least one of Equisetophyta, Angiosperm, Marchantiophyta, Gymnosperm, and Polypodiophyta, where the plant material is grown organically, or the plants are grown in the absence of synthetic fertilizer, synthetic herbicide, and synthetic pesticide. The land based plant is selected from at least one of Equisetophyta, Angiosperm, Fagaceae, Fabaceae, Poaceae, Cyperaceae, Asteraceae, Lamiaceae, Urticeae, Marchantiophyta, Gymnosperm, and Polypodiophyta. The land based plant or land based plant feedstock comprises greater than 5 wt.% of amorphous silica on a dry weight basis.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The method (M1) involves obtaining the silica from plant material; and the method further involves: reacting amorphous silica with a vaporizable reducing agent in an inert atmosphere; mixing amorphous silica with reducing agent to form a mixture; heating the mixture of amorphous silica and reducing agent to vaporize at least some of the reducing agent to initiate a reaction in which the silica is reduced to silicon, where the temperature is maintained at 450-700 degrees C, preferably at 550-650 degrees C, for the duration of the reaction; and dissolving out or leaching out from the mesoporous amorphous silicon any other reaction products using hydrochloric acid. In the method (M2), the silica is obtained from a source excluding one derived from diatoms such as diatomaceous earth. Preferred Components: The amorphous silica is mesoporous amorphous silica. The mesoporous amorphous silicon consists of amorphous silicon; and mesoporous polycrystalline silicon (less than 40 wt.%, preferably less than 10 wt.%, especially less than 1 wt.% and greater than 0.1 wt.%) or a defective phase of mesoporous silicon. The reducing agent is selected from magnesium, calcium or aluminum (preferably magnesium). The other reaction products comprise at least one of magnesium oxide and magnesium silicate. The amorphous silica is partially reduced. The mesoporous amorphous silicon produced comprises a core of mesoporous amorphous silica. The mesoporous amorphous silicon possess an oxide content corresponding to between about one monolayer of oxygen and a total oxide thickness of less than or equal to 4.5 nm covering the entire silicon skeleton. The mesoporous amorphous silicon has oxygen to silicon atomic ratio of 0.04-2, preferably 0.60-1.5. ACTIVITY - None given.    MECHANISM OF ACTION - None given.    EXAMPLE - Samples of Horsetail powder were immersed in 10% hydrochloric acid (HCl) at 100 degrees C for less than or equal to 2 hours. Subsequent to water-rinsing and drying, the powders were calcined in air at 500 degrees C for less than or equal to 2 hours, resulting in porous silica. The porous silica powders were then blended with magnesium powder in a molar ratio of 1:2 (SiO2:2Mg). The magnesium/porous silica blends were then mixed with hand-milled sodium chloride powder in a 1:1 ratio by weight. Using a belt furnace, the blends were heat-treated in argon at 600 degrees C for 1 hour, resulting in reduced powders, which were dark grey-brown in color. The reduced powders were leached in 37% HCl at 70 degrees C for 1 hour to remove residual magnesium phases, resulting in a brown mesoporous amorphous silicon powder with surface area of 8.6 m2/g; and pore volume of 0.03 ml/g.