what are some examples of natural materials?
['Biotic materials. Wood (rattan, bamboo, bark, etc.) Natural fiber (silk, wool, cotton, flax, hemp, jute, kapok, kenaf, moss, etc.)', 'Inorganic material. Stone (flint, granite, obsidian, sandstone, sand, gems, glass, etc.) Native metal (copper, iron, gold, silver, etc.) ... ', 'Other natural materials. Soil.']