three days, he was able to make siliceous lumen casts from ray 
parenchyma cells which clearly showed a number of the sur- 
face features of the inner cell walls. 
Recently, Oehler and Schopf (1971) made a ‘fossiliferous 
chert’ which approximates in general appearance the natural 
bedded cherts of Precambrian age. This was done by first 
embedding some filamentous blue-green algae (Lyngbya) ina 
gel and then subjecting the gel to temperatures of about 150 
Celsius and pressures between 2000 and 4000 bars for two to 
four weeks. 
The technique described herein employs moderately low 
temperature, essentially normal atmospheric pressure, and pH 
conditions near neutral. It is based on the reagent, ethyl sili- 
cate. The use of ethyl silicate as a silica source stems from an 
earlier unpublished study of petrifaction, begun some twenty 
years ago by one of us (ESB), and later in collaboration with H. 
Irwin. 
Chemistry 
Ethyl silicate (tetraethoxysilane) is a colorless, water inso- 
luble, alcohol soluble, flammable liquid, with a specific gravity 
of 0.93 and a boiling point of about 165 Celsius. In the presence 
of water, ethyl silicate slowly hydrolyzes to monosilicic acid, 
Si(OH)s, the principal soluble form of silicon found in nature. 
OC7H5 OH 
H5C30 - Si - OC2Hs + 4HOH = HO- Si- OH + 4CyHs5OH 
OC7H5 OH 
With increase in solution concentration beyond saturation with 
respect to amorphous silica, silicic acid will begin to polymer- 
ize to higher molecular weight species through the formation of 
siloxane bonds, ve O-Si-, and the elimination of water. This 
reaction may be represented most simply with the following 
chemical equation for the formation of the dimer. 
OH OH _ OH 
| ‘ 
HO -Si-OH + HO-Si-OH = HO- Si-O- Si-OH + HOH 
/ ! 
OH OH OH OH 
