Dendritic agate
Lapidary material SiO2
Also called Mocha stone
About it
Translucent chalcedony with black or brown tree-like dendrites of manganese oxide. Brazil and India are major sources; "mocha stone" is an old name, after the port in Yemen.
- 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
- white, grey, colourless, with black or brown dendrites
- Transparency
- translucent
- Cleavage and fracture
- none; conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.