The chemical formula of mineral Aguilarite is indicated by Ag4SeS. It is usually found crystallizing as low temperature silver mineral in deposit rich in selenium. Its type of locality usually include San Carlos Mine, Guanajuato, Mexico. It is named after Ponciano Aguilar (1853-1935), superintendent of the San Carlos Mine, Guanajuato, where the mineral was found. Aguilarite is known to crystallize in the orthorhombic system of crystal formation. In optical mineralogy, this orthorhombic crystal system comprises crystals having three mutually perpendicular axes, of which all are of different lengths.

Mineral Aguilarite has no cleavage even if it is closely evaluated under polarizing microscopes used in optical mineralogy. Aguilarite is usually found gray, iron gray or black in color that can be seen more interesting when viewed with the aid of polarizing microscopes. The specific gravity measure of the mineral is ranging from 7.4 to 7.56 grams per cubic centimeters. Most crystals of mineral Aguilarite are found opaque in appearance. Aguilarite has hackly fracture that appears jagged, torn surfaces when viewed under polarized microscopes for optical mineralogy. Aguilarite crystals are usually found massive in form that is uniformly indistinguishable crystals forming large masses. The hardness measure of the mineral when it is evaluated using the Mohs scale method is usually ranging from 2 to 3. Aguilarite mineral specimens are also found non-fluorescent. It is usually found exhibiting adamantine to metallic luster when viewed in reflected light of polarizing microscopes used in the field of optical mineralogy. Aguilarite is non-magnetic. It is also most commonly found leaving a grayish black streak when rubbed on a white porcelain streak plate. It has a very weak anisotrophism when evaluated between crossed nicols of petrographic polarizing microscopes. Aguilarite is not radioactive.