Coalstuff is the sixth of the firststuffs; its token is C. The unclefts of coalstuff contain six firstbits and six bernstonebits and, most often, six evenmotes. Coalstuff is unorelike, and its unclefts most often make four bonds with other unclefts, for which thing coalstuff can, with other firststuffs, make a great manifold of minglestuffs, which are the building blocks of life. The lore of these is called lifeworthy blendlore.
Coalstuff comes in two abiding samesteads, 12C and 13C, but 13C is much scarcer. Even scarcer still is 14C, which is lightrottish with halflife of 5,730 years. When a living thing dies, its 14C halts its renewing, and dwindles as the stuff gets older. By this means, loremasters can find the age of wood, bone, and other once-living stuffs.
Clean coalstuff comes in sundry kinds; among these are writstone and toughhurst. In writstone, the unclefts lie in loosely-bound sheets; the heart of a greystick is made of writstone, and when it is dragged along the leaf, the writstone is sloughed off to make the writer's marks. In toughhurst, each uncleft is bonded to four others in a blocklike shape, so that the icestone is nearly unbreakable. No other bulk stuff is harder than toughhurst, which is brooked as both a fair athelstone and for drillbits and sharp cutting edges.
Coalstuff gets its name from coal, in which it is the main building-block. Coal is burnt for heat and to drive steam gearworks, along with lifeworthy minglestuffs rich in coalstuff, such as wax and wood. When burnt, whether in the outer loft or in the inner fire that drives living beings, coalstuff bonds with sourstuff to make wortloft (CO2). Wortloft, in turn, is taken up by worts, which free its sourstuff and brook its coalstuff in the making of new lifeworthy minglestuffs, so that the loop can begin anew.