The methods of investigation were: XRD (diffractometer, photo-methods - in powder and single-crystal cameras), Electron Microscopy (SAD, Kevex), IR-spectroscopy and electron sond analysis.
The approximately chemical formula of the original apatite-like mineral is Ca$_{5}$(P,Si,S)$_{3}$}O$_{12}$ (OH,Cl) with symmetry P6$_{3}$/m, a = 9.51Å, b = 6.90Å. These crystals changed and were partly destroyed under the influence of the hydrothermal processes. The sample under investigation is a combination of the apatite and of product of changing - jennite with the formula Ca$_{9}$Si$_{6}$O$_{8}$OH$_{8}$.6H$_{2}$O and triclinic symmetry P1, a = 10.58Å, b = 7.27Å, c = 10.83Å, $\alpha 0= 99.6 \beta= 97.6 \gamma = 110.5^{o}$.
Mutual orientation of these minerals is:
apatite [001]
|| jennite [010], apatite (100) || jennite (001). The first
one is conditioned by closely related unit cell dimensions,
the second one - by possibility to have parallel plane
elements of every structure. Phosphorus and sulfur from apatite-
like structure are washed by natural thermal solutions with
CO$_{2}$, single Si - O tetrahedra are condensed into three-membered
chains along axis b of jennite.
The similar case was described in [1], but then the transformation product of apatite-like mineral was 14A tobermorite, ribbon Ca-hydrosilicate. The main difference between chemical formulas of jennite and tobermorite is Ca/Si (<1 in tobermorite), but anion type is three-membered Si - O chain or ribbon (according our data [2] the latter is more probable).
1. Taylor H.F.W.: Miner.Mag. 1953, 30, N222, p.155
2. Zadov A.E., Chukanov N.V., Organova N.I. et al.: Zap.Miner.
Soc. 1995, N2 (in press, in Russian).