Agate
Quartz var. Agate · Semi-Precious Gemstone / Decorative Stone
Crystal System
Trigonal, massive microcrystalline habit
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2
Formation Process
Hydrothermal or low-temperature deposition of silica-rich solutions in cavities of volcanic rocks
About This Crystal
A polished bookend or specimen featuring translucent bluish-grey chalcedony with distinct concentric banding in orange and brown, terminating in a small central cavity lined with microcrystalline quartz druzy.
Physical Characteristics
Color varies from blue-grey to orange-brown; white streak; no cleavage; conchoidal fracture; specific gravity around 2.65; brittle tenacity; typically inert under UV light
Optical Properties
Singly and doubly refractive (aggregate microcrystalline structure), refractive index ~1.544-1.553, typically exhibits no significant pleochroism
Hardness & Durability
Origin Region
Brazil, India, Madagascar, USA; found in volcanic and metamorphic rocks
Hardness & Durability
Mohs hardness of 6.5 to 7; good toughness due to microcrystalline interlocking structure; stable under normal environmental conditions
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid harsh chemicals and prolonged direct sunlight to preserve any dyed colors
Rarity & Value
Common; value depends on size, banding pattern, color vividness, and polish quality; often dyed commercially, though this specimen appears naturally colored
Special Characteristics
Features concentric color banding and a central microcrystalline quartz druzy pocket
Lore & History
Historically used as an amulet for protection and healing by ancient civilizations like the Egyptians and Greeks; associated with emotional stability, balance, and grounding in modern crystal healing