Basalt

2-2.5 usd/kg
Circularity potential
Medium
Strength
Extreme
Production energy
Low
Stiffness
High
Embodied CO2
Ultra low
Density
High

Basalt is a fine-grained igneous rock, formed from the rapid cooling of volcanic lava. It makes up nearly all volcanic rock on earth. Around 50% silica (SiO2), its chemistry is the same as slow-cooling coarse grained gabbro – the exact ingredients will vary according to the location. It is typically dark coloured, including shades of grey, through brown and black.

It is used as stone in sculpture, architecture, construction and road building. Alternatively, it is melted and extruded into a fibre, which is converted into fabrics, felts and composites. The textiles are used as reinforcement in the production of high-strength composites, as high quality sound and thermal insulation, and fireproofing.


Sustainability concerns
Non-renewable ingredients
Raw material generates polluting by-products
Low circularity potential


Fibres are produced by melting crushed rock at around 1,500 degC and drawing the molten material through small holes. Fibre diameter is typically between 10 and 20 microns – they do not pose a health risk when inhaled, like asbestos, which can split into very fine fibres that can cause very serious adverse health effects.

The fibres are stiff, strong and non-combustible. They are less strong than carbon fibre, but are stronger than E-glass and non-conductive, and so are useful for applications that require strength and radio transparency, for example. They are cheaper than carbon fibre, too, which means they may be used in applications that sit between the requirements of glass and carbon.

Fibres are used as reinforcement in composites, such as fibre reinforced concrete (FRC) used in construction and plastics used in automotive, aerospace, military and rockets. It is available with finishes that are compatible with all types of resin system, including thermosets (epoxy, polyester and vinyl ester) and thermoplastics (polypropylene, polyester and nylon). Basalt fabric is also used for insulation (called mineral wool, or stone wool, like Rockwool) and fire protection, and as a geotextile for restraining slopes.


Design properties
Cost usd/kg
2.5
Embodied energy MJ/kg
18
Carbon footprint kgCO2e/kg
0.4
Density kg/m3
2630
Tensile modulus GPa
86-90
Tensile strength MPa
3000-3850
Shear modulus GPa
21.7
Hardness Mohs
4-6.5
Poissons ratio
0.2
Thermal expansion (µm/m)/ºC
5.5
Melt temperature ºC
1450
Thermal conductivity W/mK
1.3
Temperature min-max °C
-250 to 700
Thermal
insulator
Electrical
insulator