User blog comment:Yountoryuu/Sanji vs. Aokiji and Kizaru/@comment-3202520-20110722185405

I Wonder if swords do infact work against kizaru but maybe the sword Ryuma gave Zoro is made of obsidian why i think it is:
 * the color (even tough obsidian can be of other colors)
 * the quality of the blade since obsidian is many times sharper than steel could ever wish
 * Cause obsidian was used to make primordial mirrors this way zoro could damage kizaru if he does not learn haki or gets a seastone sword(which I suspose as stone like properies so making a good blade will be really dificult)

the 3 main reason i think its made of obsidian but anyways i loved the Fight 10/10