formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...
of NaCaCu5(PO4)4Cl•5(H2O). It was first described in 1942 for an occurrence in Chuquicamata, Chile and was named after Mat Sample, a mine superintendent for the
Chile Exploration Company
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
.
Sampleite is monoclinic. It belongs to the space group ''P''21/n or ''P''21/c. In a thin section it has a high surface relief and will have sharp boundaries with the surrounding medium. Sampleite is
anisotropic
Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...
birefringence
Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefring ...
.
It is characteristically found in earthy crusts in a highly sericitized rock and is present in highly oxidized conditions near the surface. When it occurs as
micaceous
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
rosettes and aggregates it can be associated with dendrites of manganese and iron oxides. Sampleite appears to be the most recent mineral deposited with the exception of gypsum."Sampleite Mineraology." http://www.wolframalpha.com/entities/minerals/sampleite/fx/0q/75/. Retrieved 2010-11-28