Talc with E number 553b is a naturally occurring mineral in the form of magnesium silicate, which is a compound of magnesium, silicon and oxygen. Its chemical formula is Mg3Si4O10(OH)2. It is used as an anti-caking agent.
Talc can be dangerous to inhale, but is not associated with any health problems as a tablet aid. Pharma Nord uses pharmaceutical grade talc, which is checked for possible asbestos contamination.