Calcareous Sandstone / Marl
Sedimentary Clastic Rock (Calcitic Sandstone) · Mineral Specimen / Common Rock
Crystal System
Non-crystalline (Rock mass); component minerals are Trigonal (Calcite) and Trigonal (Quartz). Habit is massive and granular.
Mineral Group
Mixed; Silicates (Quartz) and Carbonates (Calcite)
Chemical Formula
Primarily SiO2 (Quartz) and CaCO3 (Calcite) with trace Fe2O3 (Iron Oxide)
Formation Process
Sedimentary; formed through the lithification of sand grains and calcium carbonate mud at low temperature and pressure.
About This Crystal
An opaque, earthy rock with a granular texture. It displays a buffet-to-greyish color with visible brown oxidation and small embedded lithic fragments. The luster is dull to earthy, and the surface is rough and porous.
Physical Characteristics
Color: Beige/Tan; Streak: White; Cleavage: None; Fracture: Granular/Uneven; Density: ~2.0-2.6 g/cm3; Tenacity: Brittle/Friable.
Optical Properties
Essentially opaque; individual quartz grains may show vitreous luster under magnification. No significant pleochroism or dispersion.
Hardness & Durability
Origin Region
Global; common in sedimentary basins such as the Colorado Plateau (USA) or the Jurassic Coast (UK).
Hardness & Durability
Variable (Mohs 3 to 7 depending on grain vs. cement); generally poor durability; susceptible to abrasion and acid erosion.
Care & Maintenance
Keep dry; avoid all acids (including vinegar) as the calcite cement will effervesce and dissolve. Brush clean only; do not use ultrasonic cleaners.
Rarity & Value
Very Common; low monetary value. Primarily used as a study specimen or industrial building material.
Special Characteristics
Effervesces (fizzes) when contacted with dilute hydrochloric acid due to the presence of calcium carbonate cement.
Lore & History
Historically used as a primary building stone for ancient architecture and cathedrals; metaphysically associated with grounding and stability in folk traditions.