Al₁₅B₆FeO₃₇Si₂

Architectural potential

An iron-doped aluminoborosilicate pushed to 1300 °C, this is a translucent mass body rather than a sheet glass — denser, harder and thermally steadier than float, and capable of five hundred megapascals of compression. Its architectural place is inhabitable translucent solid: monolithic light-admitting columns in public halls, pressed-glass treads in open stairs, structural skylight blocks that carry their own envelope load, and pier-like light wells in bath-houses or crematoria where the iron-amber body throws a warm cast across the floor. Against float glass the energy overhead drops by fifty-five per cent because the melt is held at lower viscosity with the boron flux, but embodied CO₂ runs eighteen per cent higher — so this is not a window replacement. Specify it where conventional glazing would crack, creep or lose clarity under sustained load, and where the warm iron colour is part of the design argument rather than a defect. Workshop batches cap at 500 g and the slab size is small (85×85×46 mm), so the element is a signature pier, a floor-inlay block, a light-well step — not a glazing panel. The caveat is firing: 1300 °C with a boron-rich melt demands careful crucible management and a slow anneal schedule, and medium-confidence properties mean first use should be prototyped at scale before committing to site.

Material character

The body reads a deep amber-brown with iron sitting as a dissolved colourant rather than a particulate — light passes through 46 mm as a tea-coloured translucency, clearer along the short edge, warmer and denser through the 85 mm long axis. At 3.03 g/cm³ the slab is substantially heavier than ordinary float and sits into the bench with a two-hand lift. Surface pressed-glass, with fine anneal striae legible close to the top crown; cold-cut edges show the lapidary bloom of a slow saw. A distinct step up in hardness and thermal steadiness from a soda-lime sibling — the slab rings lower and slower under a tap.