Measured heat conductivities and porosities of L chondrites at 300 K (Yomogida & Matsui 1983; Opeil et al. 2010, 2012) for which both quantities have been measured. The dashed lines correspond to the heat conductivity according to the conduction model (Appendix A.4) for a porous material with abundant micro-cracks. The indicated values correspond to the reduction factor, s, for phonon scattering length. The blue line correspond to the heat conductivity of a sand-stone like porous material according to Eq. (A.4).