"When words make noise, silence can talk."-Ernest Agyemang Yeboah
When speech is referred as silver then silence must be referred as gold. Silence is always powerful than words. Speech always ends up with arguments but silence always end with understanding. 
"When word don't make sense, silence does"
Speech is here considered as silver because when we try to speak more and more we never stop to end up with a topic instead we can be silent and we can let ever other to express out their feelings and their views. The more we try to speak the more we get into the problems because we don't know understand what we speak when we speak a lot and even we can tell something wrong which can hurt others even. Hence being silent would be rather better than talking more and more. therefore speech is considered as silver and silence as gold.