Flint
Rock
About it
Dark grey to black chert that forms nodules in chalk, usually with a chalky white rind. Its sharp conchoidal fracture made it the main tool stone of Stone Age Europe and the spark-maker in flintlock guns.
- Type
- Rock (sedimentary)
- Group
- Sedimentary (chemical)
- Hardness (Mohs)
- 6.5–7
- Specific gravity
- 2.5–2.65
- Lustre
- waxy, vitreous (glassy)
- Colours
- black, dark grey, brown, with a white crust
- Transparency
- translucent, opaque
- Cleavage and fracture
- none; conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.