Where to find
Mold is an uncommon block, but it can still occasionally be found in rather large "patches" or clusters embedded in the walls, on the floors and ceilings of large caverns on the Stalactite layer that often have pools of healing Mineral Water in them. Only some of the Caves that lead down from the surface will reach into this stratum though.
Clusters of Mold blocks can also be found embedded in large bodies of solid Stalactite layer rocks when digging through this underground layer. They often can be found rather close to clusters of Mud.
In Creativerse, all Mold blocks are already part of the template worlds that each newly created Creativerse game world is a copy of. Since Mold blocks cannot grow nor spawn, no further Mold blocks are generated in any game world after world creation.
How to obtain
Mold can be mined when you have either a Stone Mining Cell or an even stronger Power Cell equipped in the mining cell equipment slot next to your player character on the right side of the inventory/bag.
Diamond Mining Cells and Lumite Mining Cells will not lose any durability when used for mining Mold blocks. Diamond Mining Cells will lose durability though when mining blocks of Stalactite and Siltstone, only Lumite Mining Cells can mine tier 3 blocks without losing durability.
Another alternative to mine Mold instead of pulling it block by block would be to place Advanced Excavators (not to be confused with Advanced Extractors) on it. The Advanced Excavator can remove Stalactite layer blocks in the size of 7x7x7 blocks maximum. Half of the removed blocks will be saved in Loot Bags.
You can also dig through the Stalactite layer by destroying it. Strong TNT can destroy blocks from the Stalactite layer like Stalactite and Siltstone and other tier 3 rocks. Please note that TNT is a destructive Explosive that will produce a crater and will not leave any blocks behind that could be collected.
Excavators and TNT-type Explosives will remove or destroy nearly all types of crafted blocks and objects like torches, furniture, signs, windows, all crafted building blocks, stairs etc., even up to Corrupted Stone Walls. However, these area-damaging Explosives will leave all Ore Nodes intact, also all storage containers, crafting stations and any objects that can contain blocks/items, including Extractors.
You can prevent all area-damaging Explosives from being used on your game world or player claim by disabling the option "TNT enabled" on claims and/or enabling the world option "Disable Explosives".
How to use
If you want to use Mold as a building block, you might want to carefully illuminate all Mold blocks with crafted luminaires to prevent aggressive or simply unwanted Creatures from spawning.
Since update R58 on December 19th 2018, Mold can be crafted into 6 green Globs of Goo each in the Crafting Menu. The according crafting recipe can be unlocked by obtaining Mold for the first time.
Mold cannot be corrupted nor transformed in any other way in the game world.
Before update R58 on December 19th 2018, 1 block of Mold could be processed into 6 green Globs of Goo in a Processor without requiring a crafting recipe. Now, Goo can be crafted "on the fly" practically instantly from Mold in the Crafting Menu, and unlocking this crafting recipe merely requires acquisition of the first block of Mold.