Esper Signius Larsen, Jr. (14 March 1879 – 8 March 1961) was an American geologist and petrologist who contributed to techniques for age estimation using the lead-uranium ratio or Larsen method and the petrological study of non-opaque minerals using

optical microscopy Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...

techniques. He served as a professor of petrology at

Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...

from 1923 to 1949. The mineral

Esperite Esperite is a rare complex calcium lead zinc Silicate minerals, silicate (PbCa3Zn4(SiO4)4) related to beryllonite and trimerite that used to be called ''calcium larsenite''. Esperite has a white, greasy appearance in daylight and is much prized f ...

(earlier called Calcium Larsenite) was named after him.

Education and career

Larsen was born in

Astoria, Oregon Astoria is a Port, port city in and the county seat of Clatsop County, Oregon, United States. Founded in 1811, Astoria is the oldest city in the state and was the first permanent American settlement west of the Rocky Mountains. The county is the ...

to Danish immigrant Esper Signius Sr. and Louisa Pauly from Akron. His father ran grocery stores and moved to Portland where young Larsen went to study at Portland Public Schools. He then worked for a while before joining the

University of California The University of California (UC) is a public university, public Land-grant university, land-grant research university, research university system in the U.S. state of California. Headquartered in Oakland, California, Oakland, the system is co ...

in 1902 where he studied under

Andrew Cowper Lawson Andrew Cowper Lawson (July 25, 1861 – June 16, 1952) was a Scots-born Canadian geologist who became professor of geology at the University of California, Berkeley. He was the editor and co-author of the 1908 report on the 1906 San Francisco ...

and Arthur Starr Eakle. After studying mathematics and chemistry he graduated in 1906 and taught for a while. He then moved to work in geology at the

Carnegie Institution The Carnegie Institution for Science, also known as Carnegie Science and the Carnegie Institution of Washington, is an organization established to fund and perform scientific research in the United States. This institution is headquartered in Wa ...

in Washington under

Frederick Eugene Wright Frederick Eugene Wright (October 16, 1877 – August 25, 1953) was an American optical scientist and geophysicist. He was the second president of the Optical Society of America from 1918-1919. Biography He was born in Marquette, Michigan, and hi ...

and Herbert E. Merwin. Later, Larsen returned to

Berkeley Berkeley most often refers to: *Berkeley, California, a city in the United States **University of California, Berkeley, a public university in Berkeley, California *George Berkeley (1685–1753), Anglo-Irish philosopher Berkeley may also refer to ...

and received a doctorate in 1918 with a thesis on the "Areal Geology of the Creede Mining District, Colorado." In 1909 he joined

US Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on March ...

under Charles Whitman Cross, their studies on the volcanic

San Juan Mountains The San Juan Mountains is a high and rugged mountain range in the Rocky Mountains in southwestern Colorado and northwestern New Mexico. The area is highly mineralized (the Colorado Mineral Belt) and figured in the gold and silver mining industry ...

was published in 1956. Larsen was promoted from assistant geologist to geologist in 1914 and worked there until 1923 when he joined

as a professor of petrology. He taught in Harvard until 1949 and went back to work with the USGS but stopped due to poor health in 1958.

Research

Larsen's major work was an analysis and tabulation of the optical characteristics of 600 minerals using liquid immersion within a hollowed

prism PRISM is a code name for a program under which the United States National Security Agency (NSA) collects internet communications from various U.S. internet companies. The program is also known by the SIGAD . PRISM collects stored internet ...

. The results were published in 1921 and revised with Harry Berman in 1934. ''The Microscopic Determination of the Nonopaque Minerals'' (1934) was a major landmark in mineralogy. After his retirement in 1949 he focussed on the development of the aging technique based on Lead, Uranium and Thorium ratios in

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...

. The mineral Esperite was named after him (it was originally described as Calcium Larsenite and renamed in 1965).

Personal life

In 1910, Larsen married Eva Audrey Smith, daughter of Sylvester C. Smith. One of Larsen's sons was also a petrologist Esper S. Larsen III who also died in 1961.

References

External links

The areal geology of the Creede mining district, Colorado
Ph.D. Thesis, (1918)
The Microscopic Determination of the nonopaque minerals (1921)
Bulletin 679. USGS.
The Microscopic Determination of the nonopaque minerals (1934)
Bulletin 848. USGS. With Harry Berman. {{DEFAULTSORT:Larsen, Esper Signius, Jr. 1879 births 1961 deaths University of California, Berkeley alumni Harvard University faculty People from Astoria, Oregon University of California, Berkeley faculty United States Geological Survey personnel 20th-century American geologists