Explanatory notes
… by the agglomeration of quartz crystals with feldspar and mica. It varies in colour (grey, green, pink, red, etc.) … quartzose or siliceous particles naturally agglomerated by calcareous or siliceous materials. Basalt is also an igneous … ophite) which, being a natural form of magnesium silicate, cannot be classified in heading 25.15 . The stones of this …