Sponges, one of the most primitive animals, are exclusively aquatic sessile organisms. Siliceous sponges are mainly represented by two classes, Demospongiae (Sollas, 1885) and Hexactinellida (Schmidt, 1870). Their internal skeleton is composed of spicules that serve to stiffen the soft body, helping the animal with protection and anchoring. During the biomineralization process, silica plays a dominant role in skeleton formation, but nothing would be possible without organics intercession. In this study, we used solid-state NMR spectroscopy to better understand the role of organics during the biosilicification process. Our goal is to more precisely depict the organo-silica interface to discriminate the different species among the great variety of specimen. Solid-state NMR is one of the most versatile tools of characterization in materials science. However, this technique suffers from low sensitivity and long acquisition times. Natural specimen of spicules contain a big amount of silicon but a small amount of carbon (e.g., 2-7 wt% C). As no isotopic enrichment is possible and 13C isotope is only 1.1 at% nat. ab., it is difficult to collect exploitable data from carbon. 29Si and 13C NMR spectra were compared to assess the importance of the taxon.