@mcc
so everyone's gonna say obsidian, which has a long history in especially mesoamerican ritual tradition as a ritual implement material.
But.
The thing about quartz is that you can fuse it into arbitrary shapes, and ritual knives do not necessarily need to be monomolecular sharp.
So while a scalpel-edged obsidian knife is cool, that edge is going to need maintenance, which is going to be a huge pain in the ass.
But a fused quartz ritual knife can have a much more sturdy edge that won't fucking chip at the slightest nick against something else, and will be much safer to handle during rituals for most practitioners.
So as a practical consideration, I'd use a fused quartz ritual knife, if I weren't already a blacksmith who forged herself an iron one years ago lol.
However, for blog shit, they're prolly talking about https://obsidian.md/ which has a plugin that'll let you publish to a website.