Help Id problem with magnetic rock contamination

[arroyo9831]

Cleaning my glasses a lot of fragments stuck to the razor blade while cleaning algae, I can't identify what type of rock it is [came in a colony of chypastre by the bunch]. Without being able to identify her, I cannot take action.

 

[Timfish]

From what I've seen in my tanks over the years there's a surprising amount of iron fragments in sand and mud products for aquariums. I wouldn't worry about it myself.