Many products are not regulated by a governing body. Quality control is in the hands of those who use these products. For example, Figure 1 shows a white powder from a bottle labeled "talc." When this powder was run on the MiniFlex, talc was observed only in trace quantities (Figure 2). Talc is typically identified as magnesium silicate hydroxide. However, this material is primarily composed of calcite and dolomite identified as calcium/magnesium carbonate (Figure 3).
This material was intended to be used as a drying agent; therefore the intended use is still possible. However, if you were looking for a silicate source, you would not find it here.