mineral

Feldspar (likely Orthoclase or Plagioclase)

Tectosilicate Feldspar (KAlSi3O8 to (Ca,Na)(Al,Si)4O8)

AI-generated identification · may be incorrect

Hardness: 6-6.5 (Mohs); Color: Tan, cream, or grey; Luster: Pearly to vitreous; Cleavage: Two directions at nearly 90 degrees; Structure: Triclinic or Monoclinic.

Hardness: 6-6
Color: Tan, cream, or grey
Luster: Pearly to vitreous

Identified July 9, 2026More mineral →

Explore Feldspar (likely Orthoclase or Plagioclase) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6-6.5 (Mohs); Color: Tan, cream, or grey; Luster: Pearly to vitreous; Cleavage: Two directions at nearly 90 degrees; Structure: Triclinic or Monoclinic.

Formation & geological history

Formed primarily in igneous rocks like granite or metamorphic rocks. The specimen appears water-worn (tumbled), likely found in a riverbed or coastal deposit, and is associated with the Piedmont province geology near Baltimore.

Uses & applications

Large scale feldspar is used in glassmaking and ceramics. Polished or unique specimens like moonstone or sunstone are used in jewelry.

Geological facts

Feldspar is the most abundant mineral group in Earth's crust, making up about 60% of terrestrial rocks. The name 'feldspar' is derived from the German 'Feldspat', meaning field mineral.

Field identification & locations

Identified by its distinctive blocky cleavage and pearly luster. In the Maryland Piedmont region, it is commonly found in weathered granite or gneiss outcrops and stream gravels.