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 betwe ...
of NaCaCu5(PO4)4Cl·5(H2O). It was first described in 1942 for an occurrence in
Chuquicamata, Chile
Chuquicamata ( ; referred to as Chuqui for short) is the largest open pit copper mine in terms of excavated volume in the world. It is located in the north of Chile, just outside Calama, at above sea level. It is northeast of Antofagasta and ...
and was named after Mat Sample, a mine superintendent for the Chile Exploration Company.
Sampleite is monoclinic. It belongs to the
space group
In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...
''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 structural property of non-uniformity in different directions, as opposed to isotropy. An anisotropic object or pattern has properties that differ according to direction of measurement. For example, many materials exhibit ver ...
and has visible
pleochroism
Pleochroism is an optical phenomenon in which a substance has different colors when observed at different angles, especially with Polarization (waves), polarized light.
Etymology
The roots of the word are from Greek (). It was first made compou ...
and
birefringence
Birefringence, also called double refraction, 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 described as birefrin ...
.
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 fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...
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