A lump of clay makes so much sense! think about it, they are gems! gems form from clay subjected to high pressure and temperatures, and then the different minerals are what makes them different. So a clod would be an underdeveloped gem, similar to calling someone a baby, or maybe fetus would be more accurate since they are still in formation and haven’t been born. Peridot literally called Yellow Diamond an underdeveloped gem!
An important 19th century ruby and diamond branch brooch, designed as an articulated foliate spray surmounted by a bird of paradise, set with circular-cut and cushion shaped rubies, circular and rose cut diamons, pear-shaped peridots, mounted in silver and gold. Detaches into four brooches. English, circa 1880.