Chalcedony
| Colour | Blue, White, Gray |
|---|---|
| Mohs hardness | 6–7 |
| Lustre | Waxy, vitreous, dull, greasy, silky |
| Streak | White |
| Crystal system | Trigonal (quartz) or monoclinic (moganite) |
| Transparency | Translucent |
| Cleavage | Absent |
| Fracture | Uneven, splintery, conchoidal |
| Chemical formula | (silica) |
| Specific gravity | 2.59–2.61 |
What is Chalcedony?
Chalcedony is an aggregate of cryptocrystalline or microcrystalline silica, or in simpler terms, a mass of individual silica crystals that are too small to be seen without magnification. It is composed primarily of quartz, with minor amounts of intergrown moganite. These are both silica minerals with a chemical composition of SiO2, but they differ in that quartz has a more symmetrical crystal structure (trigonal) than moganite (monoclinic). Mineralogically speaking, the quartz and moganite crystals in chalcedony must grow in parallel chains, called "fibers." However, the term chalcedony may mo
How to identify Chalcedony
- Lustre: Waxy, vitreous, dull, greasy, silky.
- Hardness: Mohs 6–7 — about as hard as a steel knife.
- Streak: White.
- Habit: Trigonal (quartz) or monoclinic (moganite) crystal system.
Chalcedony in different forms
Stones often confused with Chalcedony
Frequently asked questions
How hard is Chalcedony?
Chalcedony is Mohs 6–7 on the hardness scale.
What colour is Chalcedony?
Chalcedony is typically blue, white, gray (Various).