Chert
Rock
Also called Hornstone and Novaculite
About it
Hard, fine-grained silica rock that scratches glass and breaks with smooth, shell-shaped fractures and sharp edges. Forms nodules and beds in limestone; the Gunflint chert of Ontario holds some of the oldest known microfossils.
- Type
- Rock (sedimentary)
- Group
- Sedimentary (chemical)
- Hardness (Mohs)
- 6.5–7
- Specific gravity
- 2.5–2.65
- Lustre
- waxy, dull
- Colours
- grey, white, black, brown, red, green
- Transparency
- translucent, opaque
- Cleavage and fracture
- none; conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.