Microbial biscuits of vaterite (a polymorph of CaCO3) were found in Lake Is
syk-Kul, Republic of Kyrgyzstan. Pour sections were defined from the inner
part to the outer part of these microbial biscuits: ii) a nucleus made up o
f coated discrete bacterial forms, (2) a massive coating attributed to the
calcification of the mucilaginous sheath of the bacterial community, (3) a
thick lamina composed of large fibers of vaterite, and (4) a discontinuous
external coating incorporating foreign elements such as diatoms, The origin
of these microbial biscuits is attributed to bacterial activity. The vater
ite formation seems to be related to the hexagonal structure of the mucilag
inous sheath and to the inhibitor role of the phosphorous present in the wa
ter during calcite precipitation.