Mineral identification combines structural and physical evidence.
Key knowledge
Mineral species are distinguished by composition and ordered atomic structure. Useful identification properties include hardness, cleavage, streak, lustre and density. Several properties together provide stronger identification than colour alone, which can vary with composition, inclusions or surface appearance.
Conditions and scope
Solid solution, alteration and mixed samples can complicate identification.
A field property comparison is not a complete chemical or crystallographic analysis.
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References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Steven Earle — Physical Geology, 2nd edition, BCcampus Open Education2 sources
Mineral species are distinguished by composition and ordered atomic structure. Useful identification properties include hardness, cleavage, streak, lustre and density. Several properties together provide stronger identification than colour alone, which can vary with composition, inclusions or surface appearance.
Mineral structure and composition describe constituents of geological materials.
Silicate structures organize silicon–oxygen tetrahedra as isolated units, chains, sheets or frameworks. Charge balance and compatible lattice sites constrain cation substitution; the olivine Fe–Mg series illustrates composition varying within a related crystal structure. Structural arrangement helps explain mineral properties.
Crystal structure helps explain observed mineral properties.
A petrographic microscope combines observations in plane-polarized and crossed-polarized light: relief, colour or pleochroism, cleavage, extinction behaviour and interference response help distinguish minerals. An ideal isotropic transparent grain stays extinct under crossed polarizers as the stage rotates. An anisotropic grain viewed along an optic axis can also stay dark, so persistent darkness alone does not uniquely establish isotropy or identity.
Optical response supplements macroscopic mineral properties.
In introductory geology, a mineral is a naturally occurring inorganic solid with characteristic composition and ordered internal structure. A rock is an aggregate of one or more minerals or undifferentiated mineral material. Rock identity therefore involves constituent materials and their arrangement, rather than requiring a single mineral species or one pure chemical formula.
A rock aggregate may contain multiple constituent minerals, so aggregate identification and mineral-species identification are distinct tasks.