cross section of septaria mineral stone. septarian nodules. diagenetic structure

radiant septaria mineral stone nodules cells structure aggregate amulet atomic calcite concentration minerals concretion connate crystal crystalline crystallization crystals diagenetic dispersion dolomite dragon earth fissures fossils fractures gemstone geode geology grown together hardness inorganic irregular shapes stripes limestone rock lustre marly mineralogy polished polygonal precious radial science semiprecious septarian shades brown turtle volcano