There should be basalt in space. It can support breathable air pressure at maybe 1km a wall width to UHV. The vacuum will seep into the rock. Then, the rock will outgas into the vacuum. The key is, the now outward outgassing voids exert outwards pressure along their walls. This changes the rate of vacuum seeping into the basalt. With thick enough continuous walls, the inward vacuum seepage stops. Any mild shock to the system and the UHV seeps completely through much of the time. It could be used for storing aerogels or helium balloons. It is dangerous enough to maybe be only for insect R+D for a while. Mantises are a dilemma: you don't want them dangerous to us. But they can imitate nearby creatures. They may be able to imitate birds and mammals both w/ positive forms of awareness...Granite is easier but breaks suddenly. Basalt might whoosh out in 2 seconds. Enough time for some emergency events to be enacted. If a lot of people want to be in space, this may be a viable strategy for a while.