'Modern man, in his well-lit house, knows nothing of the beauty of gold; but those who lived in the dark houses of the past were not merely captivated by its beauty, they also knew its practical value; for gold, in these dim rooms, must have served the function of a reflector. Their use of gold leaf and gold dust was not mere extravagance. Its reflective properties were put to use as a source of illumination. Silver and other metals quickly lose their gloss, but gold retains its brilliance indefinitely to light the darkness of the room. This is why gold was held in such incredibly high esteem'
Tanazaki- In Praise of Shadows.
Japanese flint-lock fire-starters. Iron with gold inlay. I think the top one is forged iron and the bottom one cast. (I'd imagine cast iron to be difficult to inlay, as it is hard and brittle, but im always getting it wrong with iron!) pics via; (they aint my hands)