Caves, as you’ll remember from my last update, are a huge new feature in Horse Isle 3. 
The interconnected network of caverns stretches under the entire surface and can be found in every biome. In some cases you can travel from one biome to another. For instance, my club TigerTon has a cave right outside its borders (go south from the Horse Traders) that starts in Rooted Caves, but from there you can travel to the caves under the nearby Wondershrooms biome.
This is handy because it lets you get topazes from the jungle areas and purple crystals from the wonderland areas! You can also see the different areas on your minimap, represented by different colors. For example, Spider Caves are purple.
Tips for traveling in Caves:
When opening caves, the more people in an adventuring party, the less energy it takes from all.
You cannot Quick-Travel into a cave but you can Quick-Travel out to any destination.
It’s a good idea to save cave entrances as Quick-Travel spots, so you can warp out and return to where you started.
Ride the bravest horse you can find, they will help you get over and around obstacles.
When in a Dangerous Paths area, it’s easier to get up the walls with a brave horse than it is by climbing – think of how it works around Ice Cliffs.
Where there are crystal shards, there are likely crystals – look around, crystals are glowing and obvious. I’ve included illustrations below.
You can open cave entrances from the inside but still need at least one other person with you in your Adventure Party.
Bring enough wood so you can use Torches! It consumes 1 piece of Wood per minute.
List of Collectible Resources:
I found this on the profile of the club “Where The Drafts Go.” A complete list of all cave types from all biomes is still in the works. Eventually I’d like to also have a list of all unique areas within the caverns but that’s going to be a BIG job.
Not all resources have a purpose yet, but I’m sure they will.
Imbuement Crystals
Red – Black Sands
Yellow – Desert
Green – Swamp
Blue – Decay
Purple – Wonderland
Ores
Coal – Fall Forest
Iron – Sandstone
Copper – Mesa
Silver – Volcanic
Gold – Badlands
Platinum – Ice
Gemstones
Amethyst – Fjords
Citrine – Stone Forest
Diamond – Savannah
Emerald – Rainforest
Ruby – Dark Forest
Sapphire – Tundra
Topaz – Jungle
Tourmaline – Salt Flats
Other Items
As of August 25, Bat Guano and Sulfur were introduced. Check these screenshots 
out to know what you’re looking for!
Guano can be found in caves under Bamboo Forest, and Sulfur can be found in caves under Volcanic regions. Both are used for making Black Powder, which can be made into Firecrackers.
Both items are much easier to find if you have your Torch lit, especially the Guano. It kind of glows just a bit compared to surrounding rocks.
Guano is at top, and Sulfur is at bottom.
Note about crystals, ores and gems:
THEY GROW BACK. It takes a couple of days for that to happen, but it will. So if someone cleaned out your favorite gathering spot, don’t despair – just mark the spot (on a hand drawn map) and come back later. Or, if you see a bunch of shards lying around, come back later – crystals may regrow.
Wild Horses:
Yes, you can catch wilds in the caves. They are rare, they tend to be small, and they tend to be brave. Below is a screenshot showing a wilds another player caught.
Interested in joining?
Click HERE or go to the HI3 site and put in my user ID, 1023. Whenever you buy your first subscription, you’ll be rewarded with 10 Esroh Essence (good for more energy) and 1000 gold dust to help you along!
More Illustrations:
Hopefully these images will help you get a better idea of the wonders that are in the deeps of the Infinite Wilds.
Mindflight 