The Baleens have a few varieties of houses, but in the areas where good sand is plentiful, along with the other supplies needed, you can't beat a good solid glass dome.
Originally, the glass domes started much smaller as cremation/burial mounds for members. But over time, they built up to become homes for the living.
OKAY SO
I did not have the energy/time to draw more for this concept but you're dead on. Not only would the types of sand change things, but the mud/clay used would have an impact as well!
I mostly went for this color because the examples of ancient "primitive" glass I could find that was clear-ish was all in the green-blue range.
The Baleens could and would also polish the glass, if they didn't want clay or mud to stick to it, unless it got baked in there, which could happen!
There would also, absolutely, be impurities, but I don't know if a seashell would be able to tolerate that much heat? I need to do more research.
(Note to self design some sea/shore critters with shells)
