Onyx vs Soapstone
Natural Material · grade comparison
Onyx and Soapstone are both natural material grades. Soapstone is the stronger of the two: tensile strength 10 MPa (1.45 ksi) against 6 MPa (0.87 ksi) for Onyx, about 67% more. Onyx is lighter (2.7 g/cm³ vs 2.95 g/cm³ for Soapstone) and Soapstone is stiffer (60 GPa vs 50 GPa). On the shop floor, Soapstone machines more easily (excellent vs good).
OnyxChoose it when weight is the constraint.
SoapstoneChoose it when strength drives the design, or when the part sees heat.
Onyx vs Soapstone: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all natural material grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all natural material grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Bulk Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Compressive Strength
Flexural Strength
Shear Strength
Fracture Toughness (K_IC)
Hardness, Knoop
Hardness, Mohs
Same in both: Shear Modulus 20 GPa2.9 Msi
Physical
Density and transition temperatures.
Density
Porosity
Melting Point (Solidus)
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Polishability
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 0%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Thermal Diffusivity
Same in both: Thermal Shock Resistance Index 0
Strength versus weight
Yield strength against density for every natural material grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | Onyx | Soapstone |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$ Standard | $$ Standard |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Onyx vs Soapstone — frequently asked
Is Soapstone stronger than Onyx?
Yes. Soapstone has a typical tensile strength of 10 MPa (1.45 ksi) against 6 MPa (0.87 ksi) for Onyx — about 67% more.
Which is cheaper, Onyx or Soapstone?
Both sit in the same relative cost tier ($$, standard); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, Onyx or Soapstone?
Soapstone. Its machinability rates excellent (90/100) against good (65/100) for Onyx.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Onyx and Soapstone side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.