Which preposition is appropriate?
coffee is made of ground coffee beans.
coffee is made from ground coffee beans.
made of: if original material is still visible.
made from: if original material has been transformed and invisible.
(Going by the above, I would choose "made of")
Not a teacher. If you took a bunch of coffee beans, drilled holes in them and strung them together into a necklace, then you could say the necklace was "made of" coffee beans.
If you take the beans, grind them into a powder, and extract the essence from the beans with hot water, then you have made something "from" coffee beans.
1) Coffee is made of ground coffee beans.
2) Coffee is made from ground coffee beans.
of originally meant 'away, away from' but came to have genitive significance as translators used it to translate 'de' and English lost genitive case marking.
from originally meant 'forward movement' but came to mean 'movement away'
of: used as a function word to indicate origin or derivation
from: used as a function word to indicate the source, cause, agent, or basis.
Given the above, I could not confidently say either 1) or 2) is wrong. They are both good.