Comments on Episode 15:
Fire Clay absolutely has special properties: if fire clay is used for ceramics it creates stoneware, which can hold liquids without being glazed. Stoneware pots are a great way to expand your booze stockpile without having to cut down massive numbers of trees for barrels or use up your stone and metal. Stoneware items are also more valuable than their earthenware counterparts, and because of how clay works it is an infinite resource: you could build a kiln and designate a "clay" activity zone over some fire clay floor, then set "gather clay" to repeat and have a massive stockpile of fire clay boulders to make pottery out of or even build from. Conveniently, prepared meals will also be stored in such pots, letting you sell prepared food to the elves, who would otherwise get fussy about the barrels.
You can still make obsidian short-swords at a craftsdwarf's shop with an obsidian stone and a log for the handle. They're not very good any more though, because for whatever reason obsidian doesn't have a great edge value.
You cannot smelt blocks, and raw whatever glass is only used as either an uncut gem or for moods that need glass including glassmaking moods. To make glass items, you need to do it straight from sand. It does look like you might have some red sand on the left side of the entrance, as there's a bright red natural wall on the surface, but I'm not totally familiar with the graphics pack.
The only real problem I see is that you probably don't have enough food-storage items (barrels or large rock or stoneware pots) around to actually get brewing done: they're all taken up holding prepared meals and raw materials like the meat your hunters bring in. You have a well, so dwarves won't die, but they might start getting cross soon if the booze doesn't flow.
All in all, another good episode. I really like seeing how the fortress takes shape, because it is so very different than my usual style, which is all narrow tunnels and long staircases in the depths.