The impregnation of a raw sisal fiber in a saturated solution of calcium hydroxide generated a fiber coated by a remarkable quantity of calcium carbonate. This composite preserves the original morphology of sisal fibers. However, some detachments of the inorganic coating are observed at microscopic level; additionally, some fiber components have been removed by the preliminary sodium silicate washing. The final composite exhibits more amorphous characteristics than the original raw fiber, as well as its mechanical behavior was similar to an elastomeric material with more homogeneous mechanical properties than the original raw fiber.