Looking at the 1st-level conjuration spell "Find Familiar" (Player's Handbook 240), it specifies the material component as "10 gp worth of charcoal, incense, and herbs that must be consumed by fire in a brass brazier." The application of the word "consumed" here indicates that the items are destroyed by the natural action of fire. "Consumed by fire" is a relatively common phrase that renders the meaning of "destroyed" (e.g., https://brooksbulletin.com/more-grassland-consumed-by-fire-in-the-county/#). Squaring that against the principle of conservation of mass, a way of interpreting the consumption of spell component materials is to assume that the matter still exists, but it is in such a high state of entropy that its energy is in a more spread out and disordered state. It would cost more energy to re-order it than it would provide. Because some energy is always lost as heat (by conduction, convection, and/or radiation), the component is essentially irretrievably altered.

Looking at the 1st-level conjuration spell "Find Familiar" (Player's Handbook 240), it specifies the material component as "10 gp worth of charcoal, incense, and herbs that must be consumed by fire in a brass brazier." The application of the word "consumed" here indicates that the items are destroyed by the natural action of fire. 

"Consumed by fire" is a relatively common phrase that renders the meaning of "destroyed" (e.g., https://brooksbulletin.com/more-grassland-consumed-by-fire-in-the-county/#).

Squaring that against the principle of conservation of mass, a way of interpreting the consumption of spell component materials is to assume that the matter still exists, but it is in such a high state of entropy that its energy is in a more spread out and disordered state. It would cost more energy to re-order it than it would provide. Because some energy is always lost as heat (by conduction, convection, and/or radiation), the component is essentially irretrievably altered.