OreSpawn 4 Geomes and Formations

Geomes and Rock Formations

OreSpawn 4 documentation: OS4 index | Player guide | Configuration reference

OreSpawn can create an underground that has broad geological structure rather than choosing a random rock for every block. It does this with geomes, rock families, depth preferences, and continuous formations.

Rock strata are optional. Ore-only providers can use OreSpawn without enabling them.

What is a geome?

A geome is a broad geological province beneath the ordinary Minecraft biome map. It influences which rock families and individual rocks are likely in an area.

Geomes are related to surface biomes, but they do not simply copy biome borders downward. OreSpawn combines:

• the biome and its configured or inferred geological influence;
• broad regional variation, which lets a province extend across many chunks;
• boundary variation, which prevents perfectly straight transitions.

This allows the surface and underground to agree without making them identical. Mountains can favour mountain-belt geology, oceans can favour coastal shelves, deserts can favour arid basins, and cold peaks can favour glacial highlands. Regional variation can still carry a province across a biome border.

Built-in geome types

OreSpawn supplies eight general-purpose geomes:

• Stable craton: a stable region suited to older intrusive and metamorphic foundations.
• Mountain belt: strongly favours metamorphic and intrusive families.
• Volcanic arc: strongly favours volcanic rocks.
• Sedimentary basin: favours broad sedimentary layers.
• Coastal shelf: favours sedimentary geology beneath oceans, shores, and nearby terrain.
• Arid basin: suits dry-region sediments and evaporite materials.
• Wetland basin: favours sedimentary geology beneath wet environments.
• Glacial highland: associates cold and elevated terrain with suitable highland geology.

Providers and modpacks can adjust these weights or define additional geomes.

Rock families and depth

Each rock belongs to one of four families:

• sedimentary;
• metamorphic;
• intrusive igneous;
• volcanic igneous.

A geome assigns weights to those families. Each individual rock can then apply its own geome weights.

Rocks also define:

• depth_peak, the preferred world Y level;
• depth_spread, how broadly the rock remains likely above and below that preferred level;
• min_y and max_y, hard placement limits;
• weight, its general selection weight.

These values are preferences, not a single fixed layer. A provider can make sedimentary rocks more common at higher levels, intrusive and metamorphic rocks more common deeper down, and still allow broad transitions and overlap.

The selection process is:

surface biome + regional variation → geome → family at this Y level → individual rock → formation

Sky and stable layers

Sky is OreSpawn's modern geology engine. New packs should use its stable_layers formation algorithm.

Stable layers give formations a persistent identity across an area. The formation controls decide:

• horizontal reach;
• vertical thickness;
• waviness;
• edge irregularity;
• continuity.

Together these create broad, bending formations instead of a noisy mixture of small pockets. A player can cross a region or descend through it and see the geology change gradually.

The older sky_v1 algorithm remains available for migrated worlds. It should not be selected for a new pack.

Cyano legacy mode

Cyano (Legacy) preserves the classic Mineralogy-style layer engine. It uses the configured rock catalogue but follows the older geome-size, rock-layer-noise, and layer-thickness controls.

Use Cyano when preserving an existing world's chosen generation style or when a pack deliberately wants the classic layers. Use Sky with stable layers for new OS4 setups.

Biomes and modded worlds

Biome influence can come from:

• explicit biome registry IDs;
• Forge biome types;
• biome names and climate characteristics used as a fallback.

Missing optional-mod biome IDs are ignored while the profile is baked. This lets a pack include compatibility rules without making every referenced biome mod a hard dependency.

Read Biomes and World Materials for biome palettes and surface or aquifer changes. Those systems are separate from geome-influenced rock strata.

Configuring formations

Players can use Recommended Defaults, presets, and the world-creation screens. Pack authors can edit the same values in an OS4 profile.

For exact fields and supported ranges, read the Configuration Reference. The guide and schemas matching the installed jar are exported to:

config/orespawn-guide/