INCI name
Talc
Also listed as: Talcum powder, hydrated magnesium silicate
Talc is a soft mineral, a hydrated magnesium silicate. It is used in loose and pressed powders, some eye products, and older-style body powders, because it absorbs moisture and reduces friction.
The long-running safety debate around talc has two separate parts. One is historical asbestos contamination of some talc mines; cosmetic talc is required, in major markets, to be asbestos-free, and reputable suppliers test for it. The other is a body of litigation and research on perineal talc use and cancer risk, which regulators have reviewed over many years and which this site does not try to settle. Loose powders also raise a simple inhalation question, as any fine dust does, especially around infants.
If you want to avoid talc, look for the INCI name Talc, not for the marketing word "talcum-free" alone, and check powders in particular.