Agate Geode Nodule
Quartz var. Chalcedony / Agate · Mineral Specimen and Semi-Precious Gemstone
Crystal System
Trigonal, microcrystalline massive habit forming globular crusts and druzy quartz linings
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2
Formation Process
Secondary formation via hydrothermal or groundwater silica-rich solutions precipitating in cavities of volcanic rocks
About This Crystal
A small, heart-shaped brownish-red nodule featuring an inner cavity lined with sparkling, translucent microcrystalline quartz crystals and chalcedony layers
Physical Characteristics
Reddish brown exterior rind, white to clear inner quartz; Mohs hardness of 7; conchoidal fracture; vitreous to waxy luster; insoluble in acids except hydrofluoric
Optical Properties
Singly to doubly refractive with aggregate birefringence, translucent to opaque body with transparent druzy crystal tips
Hardness & Durability
Origin Region
Found globally; notable deposits in Brazil, Uruguay, Mexico, and the USA
Hardness & Durability
Mohs hardness of 7, making it durable for jewelry and handling, with no true cleavage
Care & Maintenance
Wash with warm soapy water and a soft brush; avoid harsh chemicals and prolonged direct sunlight if dyed
Rarity & Value
Common and widely accessible; value depends on aesthetic natural shape like heart formations, color contrast, and cavity size
Special Characteristics
Natural hollow cavity lined with sparkling druzy crystal aggregation, frequently sought after for its heart-like pareidolia shape
Lore & History
Historically used as an amulet for protection, grounding, and balancing emotional energy; associated with the root and heart chakras in modern crystal lore