Lake Superior agate
Lapidary material SiO2
Also called Laker
About it
Red-to-orange banded agate stained by iron, formed in lavas over a billion years old and spread by glaciers. Found on beaches and in gravel around Lake Superior; Minnesota's state gemstone.
- Type
- Lapidary material
- Group
- Agate (chalcedony)
- Formula
- SiO2
- Hardness (Mohs)
- 6.5–7
- Specific gravity
- 2.57–2.64
- Streak
- white
- Lustre
- waxy, vitreous (glassy)
- Crystal system
- Trigonal
- Colours
- red, orange, yellow, white, grey, in bands
- Transparency
- translucent, opaque
- Cleavage and fracture
- none; conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.