Pyrard de Laval says in 1616: ‘(in Goa) they have no glass windows, instead very fine and straight oyster shells are used, inserted into wooden frames, allowing the light to come in as if it was of paper, as they are not as transparent as glass.'Photographer Rajan Parrikar has some pictures of Goan nacre windows, though only from the outside, alas. I imagine that accurately rendering the quality of interior light filtered through the shells would be a consummate challenge for any photographer. It brings to mind the large sheets of mica used for window panes in Spanish missions in California, another effect I would love to see in person.
I highly recommend a look at Parrikar's blog and photo galleries. The twin poles of his world seem to be Goa and Iceland, an unusual combination to say the least, but he does excellent justice to both.