We saw a few episodes ago:
Leaf creating a White Walker with what looks to be a Dragonglass dagger. It was unclear from that scene whether the stabbing itself initiates the transformation or if there are other rites being performed to create it.
However, given that both Dragonglass and Valyrian Steel are capable of destroying a White Walker, I wonder if both can also be used to create them. It seems unlikely, but am curious whether anyone can find any other evidence for an answer.
My hunch is that Valyrian Steel cannot create a White Walker because it is regularly used in combat against humans. The reason I find it unlikely is that in combat over the last 1000 years in Westeros, not a single killing created a White Walker, but the number of stabs to the heart from Valyrian Steel surely was >0.
It also seems that Dragonglass quickly fell out of use after the last long winter, due to its current scarcity in Westerosi arsenals. It also seems that even if they were used in human to human combat, they never led to the conversion of a human to White Walker much like Valyrian Steel.
So is it safe to say that:
only the Children of the Forest are capable of creating White Walkers? Is that due to other rites/magic or simply the knowledge and ownership of dragonglass that gives them this ability?
