Cobalt in Hytale is a rather unusual ore among all the available for harvesting. Technically, it’s the next metal after thorium, behind iron and copper, but its actual utility is still unclear. Tools and armor crafted from it have similar durability. For example, a cobalt cuirasson trades the respectable 27% poison resistance of a thorium cuirass for a modest 6% increase in signature attack damage. A cobalt longsword, meanwhile, has only 20 more durability (140 vs. 120).
Since the game is in Early Access, cobalt’s balance is likely not yet final. Perhaps in the future, there will be a “side” progression where different ores will have similar stats but improve different aspects of a character, such as magic or combat builds. For now, cobalt is simply a blue metal with minimal advantages over thorium. But if you need it, here’s where to look.

Where to find cobalt in Hytale
Cobalt can be found in Hytale’s icy regions, known as the Whisperfrost Frontiers. To find it, head to the snowy parts of the map. Since this is essentially the third zone of the world, you’ll need the best weapons, armor, and gear available, as well as Hytale repair kits, to keep them in good condition while exploring.
The most obvious way to find cobalt is to go underground. However, unlike copper, iron, and thorium, digging isn’t always necessary. Numerous large ice caves can be found on the surface. They can be huge, treacherous, filled with icy water and long tunnels that make it easy to get lost. If this happens, use the “Unstuck” option in Hytale’s console commands to teleport to the surface.
This is what the ore looks like – a dull blue-gray lump in blocks:

I didn’t find cobalt in abundance underground. There were numerous iron deposits, but cobalt only showed up occasionally, a single lump at a time.
Your chances of finding cobalt increase if you search mountain slopes. Once you reach the mountaintops, you may notice isolated chunks of cobalt ore protruding from the slopes. Random deposits of copper, gold, and silver are also common at higher elevations. This type of prospecting often reveals a small vein for mining, rather than isolated chunks like you might find underground.
I found the most cobalt on the less snow-covered mountain slopes, on the borders of the Whispering Frost Frontiers. Perhaps this was just luck. The main advantage is that the ore is quite visible from afar when it emerges from the rock, allowing for quick surveys of large areas and compensating for its rarity.