Fused Silica vs MgO
Glass · grade comparison
Fused Silica and MgO are both glass grades. MgO is the stronger of the two: tensile strength 100 MPa (14.5 ksi) against 50 MPa (7.25 ksi) for Fused Silica, about 100% more. Fused Silica is harder — 700 HV against 600 HV for MgO — which matters for wear surfaces and threads. Fused Silica is lighter (2.2 g/cm³ vs 3.58 g/cm³ for MgO) and MgO is stiffer (249 GPa vs 72 GPa). On the shop floor, Fused Silica sits in a lower cost tier (standard, $$) than MgO (high, $$$$).
Fused SilicaChoose it when surface hardness matters, or when weight is the constraint.
MgOChoose it when strength drives the design, or when the part sees heat.
Fused Silica vs MgO: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all glass 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 glass 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
Shear Modulus
Bulk Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Elongation at Break
Compressive Strength
Flexural Strength
Shear Strength
Fracture Toughness (K_IC)
Hardness, Vickers
Hardness, Knoop
Same in both: Hardness, Mohs 6
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Refractive Index
Light Transmission
Same in both: Porosity 0%
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)
Same in both: Min Service Temperature -200°C-328 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
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 2
Strength versus weight
Yield strength against density for every glass grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | Fused Silica | MgO |
|---|---|---|
| Default condition | Annealed Glass | — |
| Relative cost | $$ Standard | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Fused Silica vs MgO — frequently asked
Is MgO stronger than Fused Silica?
Yes. MgO has a typical tensile strength of 100 MPa (14.5 ksi) against 50 MPa (7.25 ksi) for Fused Silica — about 100% more.
Which is cheaper, Fused Silica or MgO?
Fused Silica is the lower-cost material: it sits in the standard tier ($$) while MgO is high ($$$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, Fused Silica or MgO?
Fused Silica, by a small margin. Both rate not recommended for machinability — 10/100 against 5/100 for MgO.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Fused Silica and MgO 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.