Granite BLK (Commercial 'black granite')
Additive grade
ASTM C615
Pick when maximum density, strength and a deep mirror polish matter (monuments, dark cladding, machine bases).
Values for the BLK condition
Other Granite tempers and conditions
Granite is listed in 3 conditions; see the grade overview at Granite.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
C615Default Commercial dimension-stone granite | Default choice for cladding, paving, countertops and kerbs where standard ASTM C615 / GB/T 18601 minimums apply. | — | 12 | — | — | 3 W/m·K |
BLKThis page Commercial 'black granite' | Pick when maximum density, strength and a deep mirror polish matter (monuments, dark cladding, machine bases). | — | 16 | — | — | 2 W/m·K |
Metrology / surface-plate grade granite | Use for surface plates, CMM bases and machine-tool structures needing low CTE, no burring and long-term dimensional stability. | — | — | — | — | 2 W/m·K |
What is Granite BLK?
Granite BLK is Granite in the BLK grade — pick when maximum density, strength and a deep mirror polish matter (monuments, dark cladding, machine bases). Granite BLK has a tensile strength of 16 MPa (2.32 ksi), weaker than 61% of natural material grades. Elongation at break is 0.05% and the elastic modulus is 80 GPa (11.6 Msi). Granite BLK has a density of 2.98 g/cm³ (0.108 lb/in³), heavier than 102% of natural material grades. It melts at 1,215°C (2,219 °F). C615 is the default condition FabDigit quotes; BLK is available on request or by drawing note.
Advantages
- Stiff — 80 GPa (11.6 Msi), better than 102% of natural material grades
- Polishes to a fine finish — 95/100, better than 102% of natural material grades
- Good corrosion resistance — 90/100, better than 98% of natural material grades
- Tough — resists crack growth — 1.5 MPa·√m (1.37 ksi·√in), better than 97% of natural material grades
- Conducts heat well — 2.3 W/m·K (1.33 BTU/hr·ft·°F), better than 91% of natural material grades
Limitations
- Heavy — 2.98 g/cm³ (0.108 lb/in³), worse than 102% of natural material grades
- Difficult to machine — 20/100, worse than 96% of natural material grades
- Limited ductility — 0.05%, worse than 94% of natural material grades
Granite BLK properties
Typical room-temperature values for Granite BLK; 15 are specific to this condition. Other listed values are Granite reference data and may not represent this condition. Bars are the position among natural material grades.
Physical3
Granite BLK has a density of 2.98 g/cm³ (0.108 lb/in³), heavier than 102% of natural material grades. It melts at 1,215°C (2,219 °F).
Mechanical12
Granite BLK has a tensile strength of 16 MPa (2.32 ksi), weaker than 61% of natural material grades. Elongation at break is 0.05% and the elastic modulus is 80 GPa (11.6 Msi).
Thermal5
Granite BLK is rated for continuous service to 300°C (572 °F). It conducts heat at 2.3 W/m·K (1.33 BTU/hr·ft·°F), better than 91% of natural material grades. Thermal expansion is 5.5 µm/m·K (3.06 µin/in·°F).
Electrical1
Granite BLK has an electrical resistivity of 10,000 Ω·m.
Chemical & Environmental1
Corrosion resistance is excellent (90/100), better than 98% of natural material grades.
Sustainability4
Producing a kilogram of Granite BLK takes about 6 MJ of energy and emits 0.45 kg of CO₂ — less than 78% of natural material grades. Typical recycled content is 0%.
Manufacturability2
Granite BLK's machinability is poor (20/100, worse than 96% of natural material grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Granite BLK
Is Granite easy to machine?
Diamond tooling only — gang/wire saws for blocks, diamond blades, core bits and CNC routers with copious water; avoid dry cutting (silica dust, thermal cracking).
Can Granite be welded?
Not weldable; joints are made with epoxy/polyester stone adhesives, dowels, kerf anchors or mechanical undercut fasteners.
Can Granite be formed, bent or molded?
No plastic forming — shapes are produced by sawing, splitting, flaming, waterjet and profiling; design for compression and avoid thin unsupported tension spans.
What surface finishes work on Granite?
Polished, honed, flamed, bush-hammered, sandblasted or leathered; polished faces benefit from silane/siloxane impregnating sealer, and acidic cleaners must be avoided.
Granite 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 |
|---|---|---|
| SiO2mostly as quartz 20–40 % plus feldspar-bound silica | 65 – 77 | 72 |
| Al2O3feldspars and micas | 12 – 16 | 14 |
| K2Oalkali feldspar / biotite | 3 – 6 | 4.5 |
| Na2Oplagioclase | 2.5 – 4.5 | 3.5 |
| CaOplagioclase | 0.5 – 3 | 1.5 |
| Fe2O3+FeObiotite, amphibole, magnetite | 1 – 4 | 2.5 |
| MgO | 0.2 – 1.5 | 0.6 |
| TiO2 | 0.1 – 0.6 | 0.3 |
| other oxides / LOIMnO, P2O5, accessory zircon/apatite, bound water | balance | — |
Granite BLK — frequently asked
What is Granite BLK used for?
Granite BLK is typically used for countertops and vanity tops, building facades and cladding, paving and curbing, monuments and headstones and flooring in high-traffic areas. In short: durable exterior dimension stone; low machinability, diamond only; high compressive strength.
What is the tensile strength of Granite BLK?
Granite BLK has a typical tensile strength of 16 MPa (2.32 ksi) — weaker than 61% of natural material grades. Strength varies by condition: see the 3 listed tempers.
Is Granite BLK easy to machine?
Not especially — machinability is rated poor (20/100, worse than 96% of natural material grades). Diamond tooling only — gang/wire saws for blocks, diamond blades, core bits and CNC routers with copious water; avoid dry cutting (silica dust, thermal cracking).
Can Granite BLK be welded?
Not weldable; joints are made with epoxy/polyester stone adhesives, dowels, kerf anchors or mechanical undercut fasteners.
What surface finishes work on Granite BLK?
Polished, honed, flamed, bush-hammered, sandblasted or leathered; polished faces benefit from silane/siloxane impregnating sealer, and acidic cleaners must be avoided.
Can Granite BLK be formed, bent or molded?
No plastic forming — shapes are produced by sawing, splitting, flaming, waterjet and profiling; design for compression and avoid thin unsupported tension spans.
What is the maximum service temperature of Granite BLK?
Granite BLK is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM C615/C615M — Standard Specification for Granite Dimension Stone — ASTM International (2018)
- ASTM C97, C99, C170, C880, C1354 — dimension stone test methods — ASTM International (2018)
- EN 1469 / EN 12372 — Natural stone slabs for cladding and flexural strength — CEN (2015)
- GGG-P-463c / DIN 876 — granite surface plate accuracy grades — US Federal Spec / DIN (1973)
- ASM Engineered Materials Handbook — Ceramics and Glasses (rock property tables) — ASM International (1991)
- Handbook of Physical Properties of Rocks — CRC Press (1982)
- CES/ICE embodied energy and carbon data for quarried dimension stone — Granta / University of Bath (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.