Slate C629-II
Grade
ASTM C629 · EN 12326-1
C629-II = aSTM C629 Class II
Interior flooring, wall panels, hearths and countertops; absorption up to 0.45 % is allowed, so not for freeze-thaw or de-icing salt exposure.
Values for the C629-II condition
Other Slate tempers and conditions
Slate is listed in 5 conditions; see the grade overview at Slate.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ASTM C406 Grade S3 | Softer, more absorbent slate for economy roofing, garden paving and landscape work in mild climates. | — | 12 | 0.04 | — | 2 W/m·K |
C629-IIThis page ASTM C629 Class II | Interior flooring, wall panels, hearths and countertops; absorption up to 0.45 % is allowed, so not for freeze-thaw or de-icing salt exposure. | — | 14 | 0.05 | — | 2 W/m·K |
ASTM C406 Grade S2 | Mid-grade roofing slate with slightly higher absorption and softening depth; standard commercial roofing where 100-year life is not required. | — | 15 | 0.05 | — | 2 W/m·K |
C629-IDefault ASTM C629 Class I | Densest, lowest-absorption (≤0.25 %) slate for exterior cladding, paving, sills, stair treads and freeze-thaw exposure. | — | 16 | 0.05 | — | 2 W/m·K |
ASTM C406 Grade S1 | Premium hard roofing slate (absorption ≤0.25 %, depth of softening ≤0.08 mm) for permanent roofs and heritage restoration. | — | 18 | 0.05 | — | 2 W/m·K |
What is Slate C629-II?
Slate C629-II is Slate in the C629-II grade — interior flooring, wall panels, hearths and countertops; absorption up to 0.45 % is allowed, so not for freeze-thaw or de-icing salt exposure. Slate C629-II has a tensile strength of 14 MPa (2.03 ksi), weaker than 64% of natural material grades. Elongation at break is 0.05% and the elastic modulus is 58 GPa (8.41 Msi). Slate C629-II has a density of 2.8 g/cm³ (0.101 lb/in³), heavier than 96% of natural material grades. C629-I is the default condition FabDigit quotes; C629-II is available on request or by drawing note.
Advantages
- Low embodied carbon — 0.06 kg CO₂/kg, better than 100% of natural material grades
- Stiff — 58 GPa (8.41 Msi), better than 94% of natural material grades
- High service temperature — 400°C (752 °F), better than 94% of natural material grades
- Conducts heat well — 1.9 W/m·K (1.1 BTU/hr·ft·°F), better than 85% of natural material grades
- Tough — resists crack growth — 0.95 MPa·√m (0.865 ksi·√in), better than 83% of natural material grades
Limitations
- Heavy — 2.8 g/cm³ (0.101 lb/in³), worse than 96% of natural material grades
- Limited ductility — 0.05%, worse than 94% of natural material grades
- Difficult to machine — 58/100, worse than 89% of natural material grades
Slate C629-II properties
Typical room-temperature values for Slate C629-II; 14 are specific to this condition. Other listed values are Slate reference data and may not represent this condition. Bars are the position among natural material grades.
Physical2
Slate C629-II has a density of 2.8 g/cm³ (0.101 lb/in³), heavier than 96% of natural material grades.
Mechanical12
Slate C629-II has a tensile strength of 14 MPa (2.03 ksi), weaker than 64% of natural material grades. Elongation at break is 0.05% and the elastic modulus is 58 GPa (8.41 Msi).
Thermal5
Slate C629-II is rated for continuous service to 400°C (752 °F). It conducts heat at 1.9 W/m·K (1.1 BTU/hr·ft·°F), better than 85% of natural material grades. Thermal expansion is 9 µm/m·K (5 µin/in·°F).
Electrical2
Slate C629-II is an electrical insulator with a dielectric strength of 1.5 kV/mm (38.1 V/mil) and a resistivity of 700,000 Ω·m.
Chemical & Environmental1
Corrosion resistance is very good (78/100), better than 83% of natural material grades.
Sustainability4
Producing a kilogram of Slate C629-II takes about 0.9 MJ of energy and emits 0.06 kg of CO₂ — less than 100% of natural material grades. Typical recycled content is 2%.
Manufacturability2
Slate C629-II's machinability is good (58/100, worse than 89% of natural material grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Slate C629-II
Is Slate easy to machine?
Wet diamond sawing, core drilling and CNC waterjet work well; feed slowly and support the sheet, since the cleavage planes chip and delaminate under dry cutting or point loads.
Can Slate be welded?
Not weldable — joints are made by mechanical anchors, kerf clips, hooks/nails (copper or stainless) or epoxy/polyester stone adhesive.
Can Slate be formed, bent or molded?
Shaped only by riving (hand-splitting along cleavage with chisel and mallet), trimming/guillotining and grinding; no plastic forming, and holes must be punched or drilled with clearance for thermal movement.
What surface finishes work on Slate?
Natural cleft, sawn, honed, brushed or sandblasted finishes; a penetrating silane/siloxane or colour-enhancing sealer controls staining and iron-bloom, but a mirror polish is not achievable.
Slate chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| SiO2quartz + phyllosilicate silica | 52 – 68 | 60 |
| Al2O3mica/chlorite/illite | 15 – 24 | 19 |
| Fe2O3+FeOchlorite, pyrite, hematite; source of rust staining | 4 – 10 | 7 |
| K2Omuscovite/sericite | 2 – 4.5 | 3.5 |
| MgOchlorite | 1 – 3.5 | 2.2 |
| CaOcalcite content lowers acid resistance | 0.2 – 3 | 1 |
| Na2O | 0.3 – 2 | 1 |
| TiO2 | 0.5 – 1.2 | 0.9 |
| C (graphitic/organic)gives black slate its colour; raises conductivity | 0 – 2 | 0.5 |
| S (as pyrite) | 0 – 1 | 0.2 |
| LOI / H2O+ | 2 – 5 | 3.5 |
| other oxides | balance | — |
Slate C629-II — frequently asked
What is Slate C629-II used for?
Slate C629-II is typically used for roofing tiles, flooring and paving, wall cladding, countertops and landscaping. In short: splits into thin roofing sheets; highest chemical resistance among stones; brittle across cleavage planes.
What is the tensile strength of Slate C629-II?
Slate C629-II has a typical tensile strength of 14 MPa (2.03 ksi) — weaker than 64% of natural material grades. Strength varies by condition: see the 5 listed tempers.
Is Slate C629-II easy to machine?
Reasonably — machinability is rated good (58/100, worse than 89% of natural material grades). Wet diamond sawing, core drilling and CNC waterjet work well; feed slowly and support the sheet, since the cleavage planes chip and delaminate under dry cutting or point loads.
Can Slate C629-II be welded?
Not weldable — joints are made by mechanical anchors, kerf clips, hooks/nails (copper or stainless) or epoxy/polyester stone adhesive.
What surface finishes work on Slate C629-II?
Natural cleft, sawn, honed, brushed or sandblasted finishes; a penetrating silane/siloxane or colour-enhancing sealer controls staining and iron-bloom, but a mirror polish is not achievable.
Can Slate C629-II be formed, bent or molded?
Shaped only by riving (hand-splitting along cleavage with chisel and mallet), trimming/guillotining and grinding; no plastic forming, and holes must be punched or drilled with clearance for thermal movement.
What is the maximum service temperature of Slate C629-II?
Slate C629-II is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM C629 Standard Specification for Slate Dimension Stone — ASTM International (2018)
- ASTM C406 Standard Specification for Roofing Slate — ASTM International (2015)
- ASTM C120 / C121 / C170 / C217 (flexure, absorption, compression, weather resistance of slate) — ASTM International (2016)
- EN 12326-1 Slate and stone for discontinuous roofing and external cladding — CEN (2014)
- GB/T 18600 (2009)
- CRC Handbook of Physical Constants / Rock Physics & Phase Relations — AGU / CRC Press (1995)
- Dimension Stone Design Manual — Natural Stone Institute (MIA+BSI) (2016)
- Inventory of Carbon & Energy (ICE) v3 — stone — Circular Ecology (2019)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.