Yewnock's notes on crystals is obtained during The Path of Glouphrie quest. It is found by searching a chest in the northeast room of the Gnome Village Dungeon.
Yewnock was an engineer like his father Oaknock. He created the anti-illusion device for the Tree Gnome Village based on his father's notes. He also modified the singing bowl to create crystal chimes.
While creating the new anti-illusion device for the Tree Gnome Village from father's notes, I found some interesting snippets about elven magic. The lore that my father has gleaned from the elves if fascinating, and a tribute to his charm and patience—it is not easy to persuade creatures as long-lived as elves to get to the point! Father has shown that small crystal seeds may be grown into more than one enchanted artefact. This is a very different means of crafting magical items than is known to most gnomes. It seems to be that, using a static object such as the chanting mechanism (like the singing bowls), can only produce one type of item - the pitch of the bowl's ring defines the nature of the crystal object it forms. Since some elves can use their own voices to mould crystal, they can modulate their chanting to create many different items. Father has heard these, and describes them as the most beautiful songs he has ever heard - it must be amazing to hear a true chanter sing. I suspect this is an ability the elves keep to themselves. Us mortals must rely on these static crystal-shaping devices to sing for us. It also seems clear that if you 'overcharge' a crystal item by producing the same chant, except much louder than normal, you can revert the crystal to seed. This will happen anyway if the magic is drained away. My father also seemed to think that different-sized seeds were used by elves to do different things. The larger ones were used for weapons, and the smaller ones for tools. Father had one of the small ones that he had turned into a crystal saw; very useful. He seemed to think the same seed could be turned into other similarly-sized devices with the right chant. One other point he notes - since the singing bowl is also elf crystal - if you knew how to create the right song, you could use a singing bowl to make another singing bowl. One could also craft some other type of artefact or device that could itself chant, a musical instrument for example, though what other uses the chant could have apart from moulding crystal was still unknown to my father, though I believe he may have done some experimentation on the matter.