Can you explain the analogy of the stone and the gem from Chapter 19 in the context of a Guru's teachings?

The analogy of the stone and the gem illustrates how different disciples respond to the same spiritual guidance. In Chapter 19, it's noted that both a stone and a gem are polished on a whetstone, but with vastly different results. The gem becomes a brilliant, sparkling jewel, while the stone merely becomes smooth, remaining a stone. This metaphor suggests that a Guru provides the same process or teaching to all, but the outcome depends on the disciple's inherent quality and readiness. A disciple with the innate potential and virtues like faith and patience (the 'gem') will be transformed into something brilliant, while one without that inner capacity (the 'stone') will only receive a superficial benefit.