Beatha silk

The beatha, the trees that grow on the islands of Ceòthach Eilean, do not only provide housing and furniture, but also fibres for clothing. The long, silvery leaves of the beatha are the source of those fibres. The thread that results from twisting and pulling beatha leaves is almost translucent, soft and glowy.
The fabric made of this thread is shimmery, and even humans can detect various colours as the sunlight reflects on it. Depending on the season and the humidity, its hues can be golden, silvery, pale green, or even reddish. It is soft and thin, not made for cold climates, but perfect for the always warm and humid islands where the uiledath live. Because of how the leaves react with the humidity, the fabric retains its elasticity and form for years, is very hard to rip, and can repair itself in a small scale. It is unknown to humans whether it is because of some magic, the connection of the uiledath with their beatha, or because of beatha's natural properties, but the clothes made of beatha silk can actually grow to accommodate the growing body of an uiledath child, or changes in weight.
Beatha silk is seldom exported, and loses most of its properties outside the islands. Just like the beatha trees cannot grow outside of Ceòthach Eilean, beatha silk slowly loses its elasticity and shimmer away from the islands, as well as its ability to self-repair and adjust to the wearer. After a couple of years, it begins drying up and cracking. The same thing happens with beatha thread. The few efforts made by reluctant uiledath sailors and curious human merchants for the export of beatha silk thread, ended up with a series of complaints from customers, since the thread faded and broke a few months after it was taken outside the islands.