longprismatic

Longprismatic is a mineralogical term describing crystals whose growth habit is dominated by prism faces and elongated along a principal axis. The attribute is used to distinguish elongated prismatic crystals from shorter prisms, tabular, bladed, or massive forms. The term is often hyphenated as long-prismatic and appears in descriptive catalogs and older mineralogical literature.

Crystal habit: In long-prismatic crystals the prism faces are well developed and the length exceeds the width by a notable margin. In hexagonal and tetragonal systems, elongation typically occurs along the c-axis, yielding slender prisms with cross-sections that may be hexagonal or rectangular depending on the crystal system. The basal end faces are comparatively smaller.

Formation and occurrence: Long-prismatic habit arises from anisotropic growth rates caused by crystallographic structure and environmental conditions such as temperature, solution composition, and supersaturation. It is commonly observed in minerals that crystallize from hydrothermal solutions or pegmatitic environments where extended growth along one axis is favored.

Examples and notes: Many prism-form minerals can display a long-prismatic habit under suitable conditions; quartz and tourmaline crystals are frequently cited in collections as exhibiting elongated prismatic forms. The long-prismatic description is a descriptive habit term rather than a strict mineralogical category, and individual specimens may vary with impurities and growth history.

See also: crystal habit, prism, prismatic crystal, mineralogy.