|This article is about an older version of DF.|
|This article or section contains minor spoilers. You may want to avoid reading it.|
Semi-Molten Rock (SMR), represented by the tile
░, is generally found at the bottommost edges of Great magma seas. Anywhere that magma is found rests on layer after layer of semi-molten rock, with no normal material to be found beneath it. There is also a layer near the bottom of the map composed almost entirely of semi-molten rock even where magma does not overlie it. Freestanding formations are possible, though less common. Though its name suggests the rock is hot, it is not dangerous to nearby dwarves. SMR acts as a barrier, and cannot be mined through, nor smoothed. Unlike magma, SMR does not react with water, producing no steam or obsidian.
The floor under a magma reservoir, above the semi-molten rock, is described as a magma flow, appearing in blue text when examined with the Loo cursor and resembling a river of magma slowly flowing to the south (just like it did in older versions). The floor of the layer above the SMR at the bottom of the map is not a magma flow when stone is dug into, but appears as the same type of rock as the tile dug into. However, if a channel is dug down into the SMR from this tile, a magma flow floor is revealed; under this intact floor a ramp will appear, if and only if the tile of SMR was previously unrevealed. Otherwise it will be unchanged. (As a result no two of these ramps can adjoin) A magma flow also cannot be dug into, nor smoothed. However, constructions can be built on top of it, and these convert the magma flow into some other kind of stone or soil, which is sometimes useful sand or clay, appearing when the construction is removed. Curiously, water dumped onto a magma flow with magma on top of it will not turn it into obsidian; rather the magma is simply removed. At the bottom of a magma reservoir with only small amounts of water falling in, such a tile can change from 7/7 to 0/7 and back in a few single step increments with the "." key. A construction (such as a stairway up) can be designated atop the magma flow when it is momentarily is free of magma due to water falling from above. Strangest of all, once designated, a dwarf can build this construction unhindered, without any job cancellations. Once the construction is present, magma and water can react in the square, destroying the construction and converting the square into unmined obsidian.
These odd exceptions to the normal rules means that dwarves on a level partially filled with water can (with much effort) completely wall off the region surrounding some special point of interest, eventually removing all the magma from a large area despite the failure of the usual magma-water interaction.
If the stone floor which replaces a magma ramp under a built and removed construction is channeled into a second time, the ramp below becomes visible from above. Unfortunately, for some reason dwarves still cannot descend into this square with the ramp, nor can they ascend out of it should they find themselves somehow there. A dwarf dumped into the space, say, by a remote controlled hatch "accident", cannot construct anything because the adjacent squares remain semi-molten rock, and won't turn to ramps if channelled from above. Therefore an up/down stairway cannot be constructed in this space, even if it is beneath another up/down stairway. (Perhaps with some magma and water you might dig one out...) A dwarf in this space also refuses to remove the ramp or to dig in any other way... except to channel downward, which can reach hidden fun stuff by a non canonical route. Suffice it to say that the denizens of the space below seem to have trouble believing that dwarves could make it through semi-molten rock.
Semi-molten rock is not synonymous with warm stone, although any given tile of SMR may in fact be warm if it adjoins magma. If you're looking for magma and you find SMR rather than warm stone, your best bet is to do some exploratory mining several Z levels up.
In places where there is a single layer of semi-molten rock on the map, it can be safely dug through by designating a ramp in an unrevealed SMR tile one level down and one tile across from an access square.
You can also dig up into semi-molten rock just fine (by designating an up/down staircase accessible from below). This also works only if the tile is still unrevealed. But often (but not always) you can't get down there without encountering hidden fun stuff first.
Digging a ramp into unrevealed SMR may open it into an Eerie Glowing Pit.