looks cool…
Asker: Dominic, 12 years old

Answer
Dear Dominik
With only a photo available it is not always possible to identify a mineral with 100% certainty, but in this case it is probably the mineral hornblende.
Answered by
prof. Robert Speyer
Geology – Paleontology – Paleoclimatology. You study geology in Leuven!
Catholic University of Leuven
Old Market 13 3000 Leuven
https://www.kuleuven.be/
Old Market 13 3000 Leuven
https://www.kuleuven.be/
.