Eesliite

Eesliite is a hypothetical mineral species used in mineralogy pedagogy to exemplify documentation standards for new minerals. It is described as a rare silicate with monoclinic crystal symmetry, forming in high-temperature, hydrothermal metamorphic environments. The name derives from the fictional Eesli region.

Its approximate chemical formula is (Ca, Fe2+, Mg)2Si2O7 with trace Ti and Al. It crystallizes in the monoclinic system, space group C2/m. Crystal habit is usually tabular to prismatic, commonly forming aggregates.

Eesliite is typically pale green to olive in color, with a vitreous luster and a Mohs hardness of about 5.5–6. It has a density of 3.5–3.8 g/cm3. It occurs in hydrothermal veins within metamorphosed carbonate rocks and is associated with calcite, quartz, epidote, and serpentine.

The mineral was described in hypothetical educational materials to illustrate naming conventions for new minerals; the name honors the Eesli region as a nod to the exploratory context (fictional). No natural deposits are confirmed in the real world.

Because eesliite is fictitious, it has no commercial use, but it is used in teaching to demonstrate mineral description, data tabulation, and classification. It is of interest to crystallographers for illustrating monoclinic symmetry and silicate frameworks.