This is an Yggdrasil?
It's a huge ash tree in Norse mythology that overspreads the world and binds earth, hell, and heaven together. You'll see this a lot in THE SUNSTONE BROOCH. 
So this is how it's pronounced:
Pig without the P = igg
Drop without the P = dro
Silk without the K = sil
igg-dro-sil
I am TOTALLY STOKED about this book! I am eagerly awaiting the audio version in May. I read where you wrote that some of the more recent audiobooks didn’t sell as well and you were not going to be able to produce more, and I am delighted there will be more! I know the narration is different, and some folks preferred Teri (who is amazing!), but I want to stress how much I enjoyed both a male and female narrator. Marnye Young and Patrick Zeller did a great job with Topaz and I know Sunstone will be wonderful, too!
I buy both the Kindle Version and the Audible. I’m also waiting for the Audible Version, already read it on my Kindle.