Silk is found in Scorched Earth desert biomes. It's used for crafting Desert Cloth Armor and Whip.
Node yields assume the base harvest HP from game data (e.g. 1000 for Redwood trees, 620 for Metal nodes). In-game, trees and rocks with bAllowHarvestHealthScalinghave per-instance HP that varies with the node's size, so actual yields per node will vary. The values shown represent the average.
The Dire Bear is the best Silk farmer with a 10x gather multiplier from game data. The Thylacoleo is the runner-up with 10x.