Flint
Quartz var. Flint · Mineral Specimen / Sedimentary Stone
Crystal System
Trigonal, microcrystalline (cryptocrystalline) habit forming as nodules or masses
Mineral Group
Silicates (Subgroup: Tectosilicate)
Chemical Formula
SiO2
Formation Process
Sedimentary, forming through the chemical replacement of calcium carbonate in chalk or limestone by silica-rich fluids at low temperatures and pressures
About This Crystal
An opaque, nodular sedimentary rock composed of microcrystalline quartz with a smooth, chalky outer cortex and a dark, bluish-black to grey interior displaying sharp conchoidal fracture
Physical Characteristics
Color ranges from dark bluish-grey to black with a white or pale grey chalky cortex; streak is white; no cleavage; fracture is distinctly conchoidal; specific gravity is approximately 2.60 to 2.65; tenacity is brittle
Optical Properties
Singly or micro-doubly refractive with aggregate birefringence, vitreous to waxy luster on fractured surfaces, and completely opaque in mass
Hardness & Durability
Origin Region
Found worldwide, prominently in chalk deposits of Western Europe (such as the UK, France, and Denmark) and North America
Hardness & Durability
Mohs hardness of 7, high toughness due to microcrystalline interlocking structure, very stable against common chemicals and environmental factors
Care & Maintenance
Easily cleaned with warm soapy water; very durable and resistant to scratching, requiring no special storage precautions beyond avoiding extreme impacts
Rarity & Value
Common, widely accessible worldwide with low commercial value, primarily collected as geological specimens or used historically for tools and fire-starting
Special Characteristics
Produces sparks when struck against steel due to its hardness and microcrystalline structure, historically prized for creating fire and knapping into stone tools
Lore & History
Historically utilized by prehistoric humans extensively during the Stone Age for creating sharp cutting tools, arrowheads, and hand axes; associated in traditional lore with protection, cutting away negative energy, and grounding (noted as traditional beliefs rather than scientific claims)