Trying to mine Musgravite

I am in the hotspot of the rocky rings to mine musgravite but after 15 minutes there not a single asteroid has musgravite. What am I missing friends?

https://preview.redd.it/gb5baj0yn1bf1.jpg?width=2560&format=pjpg&auto=webp&s=7b5b5c3cc2b335fe06dca6d5912f5d73c35f50e6