श्वेतं स्निग्धं मृदु च श्रेष्ठम् ॥ कZ_०२.१३.११ ॥
śvetaṃ snigdhaṃ mṛdu ca śreṣṭham
The best (silver) is white, lustrous/unctuous, and soft (malleable).
They provide field-ready inspection criteria for officials, enabling consistent acceptance/rejection without specialized devices.