Lydite (Touchstone)
Silicon Dioxide (Microcrystalline Quartz variety Jasper/Chert) · Mineral Specimen / Decorative Stone
Crystal System
Trigonal symmetry; massive/cryptocrystalline habit
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 with carbon and manganese inclusions
Formation Process
Sedimentary/Metamorphic; typically forms as a fossilized marine ooze or via hydrothermal replacement of limestone/shale, often undergoing mild metamorphism to increase toughness.
About This Crystal
An opaque, fine-grained, velvet-black to dark grey variety of jasper or chert. It features a dull to waxy luster and a smooth, dense texture with occasional lighter grainy inclusions.
Physical Characteristics
Color: Black/Deep Grey; Streak: White; Cleavage: None; Fracture: Conchoidal to splintery; Specific Gravity: 2.6-2.7; Fluorescence: Usually inert.
Optical Properties
Opaque; Refractive Index: approximately 1.54 (standard quartz range); No birefringence or pleochroism visible due to opacity.
Hardness & Durability
Origin Region
Found globally; notable historical sources in Greece (Lydia), USA, and Germany. Found in sedimentary basins.
Hardness & Durability
Mohs Hardness: 6.5 - 7; Very High toughness; very stable against chemicals and sunlight.
Care & Maintenance
Extremely durable; can be cleaned with warm soapy water. Resistant to most household chemicals but can be scratched by topazes or diamonds.
Rarity & Value
Common mineral; low monetary value as a raw specimen. Value is primarily functional for assaying or as a lapidary material.
Special Characteristics
Historically used as a 'touchstone' for testing the purity of gold and silver through the color of the streak left on its surface.
Lore & History
Used since ancient Greece (Lydia) for gold smithing. In metaphysical traditions, it is considered a stone of protection, grounding, and truth-seeking.