Black specks on white ceramic tableware are not always iron spots. Iron spots usually come from iron-bearing particles in clay, feldspar, or other raw materials, as well as metal contamination introduced during mixing, conveying, or processing. During firing, these particles may oxidize or melt, leaving black, brown, or reddish-brown marks on the white body or light-colored glaze.

On speckled, reactive, or particle-effect glazes, evenly distributed spots that match the approved sample may be an intended decorative feature. On standard white tableware, isolated dark marks, raised particles, or contamination stains are normally treated as appearance defects.

During inspection, buyers should check the number, size, position, and surface condition of the spots, especially around cup rims, bowl interiors, and plate centers. Approved samples and agreed defect limits should be established before mass production. The exact source cannot be confirmed by color alone and may require raw-material screening, magnetic separation, equipment cleaning, and production analysis.