Enchantment rate modifier
Enchantment Rate Modifier is a predetermined chance between 1 - 100% for a resource node in a zone to appear in an enchanted variant (uncommon, rare or exceptional)
Every area has its own value with some areas being better than others for resource gathering.
Periodically the game rerolls resource nodes, so a resource node can spawn, despawn, or remain spawned. It also rerolls its enchant, so the enchant can increase, decrease, or stay the same.
The rarity of an enchantment depends on the enchantment rate of the zone. It can be viewed for every zone at the top of the zone map (default key N). Detailed information about the spawn chance of every enchantment can be viewed by hovering on the indicated area.