Double post
BUMP.
Still looking for glowing chamber.
*Spoilers!!*
Search under mountain spots, usually the chambers are 3-12 z levels above the lowest z level. There are plenty of trace veins spanning the z levels above the chambers, these are small veins and they're pretty safe game. If you hit thicker veins you'll know the chambers aren't too far off. Try mining upwards once you find anything at all and start excavating from the top.
The best way to find the stuff is to make large square mining designations. Hold shift, drag across an area, repeat horizontally and vertically a few times until you have a nice area of square lines designated.
Once you find some you "rake" the area, basically strike lines horizontally or vertically, each separated by 2 squares so you end up revealing everything. As precaution, you would want to avoid joining these tunnel lines except atleast at one of their ends to let you miners actually get to them. You should make sure there will be only 1 thin entryway to the site since you'll have to scramble to block off all exits if you unearth something by accident. You CAN'T build walls in the chambers or close to them, but you can still build walls a ways away. It is entirely possible to have a miner switch to mason (while removing all other masons via their labors) and having that miner build a wall before the chamber things even notice.
