Indigestible carbohydrates often are classified as fiber. the human digestive tract lacks the enzymes to hydrolyze the bonds in these polysaccarides.

Unable to hydrolyze Beta 1-4 linkages

Cellulose is present in the plant structure. It is insoluble in water and aqueous solution. Humans do not have the necessary bacteria in their intestines that produces the enzyme cellulase required to break down the beta 1,4 linkage of cellulases. So we cannot break down the bond and are unable to digest these polysaccharides.

the answer to your question is a plant

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.