Please see external links for images of buttons (front & back) made from the material(s) in question. ("NBS name" refers to labelling used by the National Button Society, USA.)
Natural materials
Animal-derived bone horn horsehair ivory leather pearl shell (Images of buttons made from all the shell types listed below) seashells:
land shells: emerald green snail shell
plant-derived
Rocks and minerals (or predominantly mineral-derived substances)
Synthetic materials
plastics
synthetic fibres synthetic textiles
See also Button collecting History of technology Seashells in personal adornment
References
Bibliography Luscomb, Sally C. (2003). The Collector's Encyclopedia of Buttons. Atglen, PA: Schiffer. p. 242. ISBN 0-7643-1815-2. LCCN 2003101645. Osborne, Peggy A. (1997). Button, button : identification and price guide. Atglen, PA: Schiffer. p. 167. ISBN 0-7643-0082-2. LCCN 92063104. Peacock, Primrose (1978). Discovering old buttons. Discovering series; no. 213. Rosemary Godsell (illus.). Aylesbury, UK: Shire Publications. pp. 76. ISBN 0-85263-445-5. Wisniewski, Debra J. (1997). Antique & collectible buttons : identification & values. Charley Lynch. Paducah, KY: Collector Books. p. 168. ISBN 0-89145-711-9. LCCN 97122120.