Sodium Sulfide / T-56

I got the items to make T-56 selenium sulfide toner and have a question about the sodium sulfide. The formula I have calls for "Sodium Sulfide (pure)" and what I obtained are fused flakes with a label that says "Assay (Na2S..aprox 60%)". Can any chemistry guru out there tell me if this is the right stuff, since the formula did indicate pure?

Thanks!
Mark