Samuelsonite is a complex mineral that is found near North Groton,

Grafton County, New Hampshire Grafton County is a county in the U.S. state of New Hampshire. As of the 2020 census, the population was 91,118. Its county seat is North Haverhill, a village within the town of Haverhill. Until 1972, the county courthouse and other offices ...

, US. Additionally, it is most commonly found as a secondary mineral in

granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...

. Samuelsonite is named after Peter B. Samuelson, a

prospector Prospector may refer to: Space exploration * Prospector (spacecraft), a planned lunar probe, canceled in 1962 * ''Lunar Prospector'', a NASA spacecraft Trains * Prospector (train), a passenger train operated by the Denver & Rio Grande Western ra ...

from

Rumney, New Hampshire Rumney is a New England town, town in Grafton County, New Hampshire, Grafton County, New Hampshire, United States. The population was 1,498 at the 2020 census. The town is located at the southern edge of the White Mountain National Forest. History ...

. The mineral has a pale yellow color and has a hardness of 5 on

Mohs scale The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by th ...

. The crystal is generally yellow, flat, and with straited

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s and blue trolleites. Samuelsonite is monoclinic. There are three vectors of unequal length in this crystal system. The three vectors form a rectangular prism with a parallelogram at the base. Therefore, two of the vectors are perpendicular, while the third makes an angle that is not equal to 90°.Rapp Jr. G.R., Campbell, T.J., and Roberts, W.L. (1990) Enclycopedia of Minerals (2nd Edition) 797 p. Library of Congress Cataloging, Washington, D.C. Samuelsonite has biaxial birefringence (trirefringence), meaning when light passes through the optic axis it is split into two rays due to the difference in refractive index of the ray with parallel polarized light compared to the ray with perpendicular polarized light.

References

Monoclinic minerals Minerals in space group 12 Phosphate minerals {{phosphate-mineral-stub