Learn the difference between scoria and clinker rock. Discover how volcanic and coal-burned formations differ, and why Wyoming clinker is perfect for aquariums and decor.
By ScoriaSupply
Filed under: Geology, Education, Product Origins
By ScoriaSupply
Filed under: Geology, Education, Product Origins
🪨 The Short Answer
Scoria and clinker are two names for the same type of rock — both formed when intense heat transforms sedimentary rock or shale into a lightweight, porous material.
The difference lies mostly in how and where the heat came from:
- Scoria usually refers to volcanic rock formed by cooling lava.
- Clinker describes coal-burned rock — naturally baked by underground coal seam fires.
At ScoriaSupply, our material is clinker, a non-volcanic scoria created right here in Wyoming’s ancient coal fields.
🌋 What Scoria Means Geologically
In geology, “scoria” comes from the Greek skōría, meaning “rust” or “slag.”
It’s used to describe porous igneous rock — the bubbly, vesicular material ejected from volcanic vents.
- Common in lava fields and basalt flows
- Light, reddish or black color from oxidized iron
- Full of air pockets from escaping gases during eruption
Volcanic scoria is mined in places like Hawaii, Iceland, and New Mexico. It’s lightweight, inert, and often used for landscaping or filter media.
🔥 What Clinker Means
Clinker, on the other hand, forms when underground coal seams ignite and burn for decades or centuries.
The intense heat (often exceeding 1800°F / 980°C) “bakes” the surrounding shale and sandstone layers, fusing them into lightweight rock.
This process creates:
- Red, black, and orange coloration (from oxidized minerals)
- Porous textures similar to volcanic scoria
- Bands, bubbles, and fused minerals unique to burned formations
Clinker ridges are found throughout the western U.S., especially in Wyoming, Montana, and the Dakotas.
It’s the same fiery transformation — just from within the Earth, rather than from a volcano.
⚖️ Scoria vs. Clinker: Side-by-Side
| Property | Scoria (Volcanic) | Clinker (Coal-Burned) |
|---|---|---|
| Formation | Cooling lava with trapped gases | Sedimentary rock baked by coal fires |
| Composition | Basaltic/igneous | Shale, clay, sandstone (fused) |
| Origin | Volcanic vents | Underground coal seams |
| Texture | Highly vesicular | Porous to semi-glassy |
| Color | Red to black | Red, orange, brown, black |
| Typical Locations | Hawaii, New Mexico, Iceland | Wyoming, Montana, Dakotas |
| Common Uses | Landscaping, concrete, filters | Aquariums, terrariums, planters, decor |
🏔️ Why It Matters for ScoriaSupply
Our product is true natural clinker — often called “scoria” because it shares the same lightweight, porous properties that make volcanic scoria so useful.
The difference is origin:
Our material tells the story of Wyoming’s ancient underground fires, not volcanic eruptions.
It’s locally sourced, environmentally responsible, and entirely unique to the coal-rich plains of the American West.
💧 Practical Uses (Same as Scoria)
Even though the geological origin differs, the benefits are the same — or better:
- Excellent for aquariums and filtration
- Great substrate for terrariums and planters
- Beautiful natural texture for decor or landscaping
- pH neutral after rinsing
- 100% reusable and long-lasting
🪶 A Material with a Story
Scoria and clinker are more than just rocks — they’re physical records of transformation.
One from fire that erupted outward, and the other from fire that burned within.
Both tell the story of heat, pressure, and renewal.
At ScoriaSupply, we embrace that story — and every bag of clinker we send carries a small piece of Wyoming’s fiery past.
🛒 Learn More or Shop Now
- About Scoria — the science behind formation
- Use Cases — see how to use it in aquariums, terrariums, and planters
- Shop ClinkerFine™
- Shop ClinkerMedium™