Daniel Tilas (11 March 1712 – 17 October 1772) was a Swedish mineralogist, mine expert, and an early pioneer of geology. The word

feldspar Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...

was coined by Tilas although spelled as ''feldspat'' in the original. He was also among the early observers of

stratigraphy Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithost ...

. The mineral

Tilasite Tilasite is an arsenate mineral gemstone, with the elemental formula Calcium, CaMagnesium, Mg(Arsenic, AsOxygen, O4)Fluorine, F. It prefers the monoclinic form of crystal, and has Mohs scale of mineral hardness, Mohs hardness of 5. It was named in ...

is named after him. Tilas was born in Gammelbo,

Västmanland Västmanland ( or ) is a historical Swedish province, or , in middle Sweden. It borders Södermanland, Närke, Värmland, Dalarna and Uppland. Västmanland means "West Man Land" or, less literally, "The Land of the Western Men", where the "we ...

where his father Olof was a wealthy landowner, titled knight in 1719 and his mother Maria was daughter of the scientist

Urban Hjärne Urban Hjärne (20 December 1641 – 10 March 1724) was a Sweden, Swedish chemist, geologist, physician and writer. Biography He was born at Skworitz near Nyenschantz in Swedish Ingria. He was the son of vicar Erlandus Jonæ Hiærne (1596� ...

. He was educated at home by tutors before going to the

University of Uppsala Uppsala University (UU) () is a public research university in Uppsala, Sweden. Founded in 1477, it is the oldest university in Sweden and the Nordic countries still in operation. Initially founded in the 15th century, the university rose to s ...

in 1723 where he studied natural sciences and Latin, interacting with

Carolus Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

. Tilas became an assistant in the Office of Mines in 1732 where he was involved in administering the Swedish mining industry. He began to map mineral resources and then saw a need to produce a geological map. He inspected mines across the region and made collections of rocks and minerals. Unfortunately, the collections and his notes were destroyed when his house caught fire in 1751. He served in the Border Commission and walked the entire stretch between Sweden and Norway from Värmland to Tornio, Lapland. Tilas used the word feldspat do describe the common mineral feldspar in 1740. Hollis Dow Hedberg noted that Tilas had come up with the idea of stratigraphy based on observations in Siljan, where hydrocarbon deposits were thought to have been pushed under the surface by a Devonian meteor impact. He hypothesized, based on his observations of petrochemical deposits, that they were at the same depth across various places, making the case for mapping as a means for identifying new locations for mining. Tilas also suggested that large erratic boulders of geology unconnected to a region may have been moved through drifting sea ice which was later explained in 1795 by

James Hutton James Hutton (; 3 June Old Style and New Style dates, O.S. 1726 – 26 March 1797) was a Scottish geologist, Agricultural science, agriculturalist, chemist, chemical manufacturer, Natural history, naturalist and physician. Often referred to a ...

as having been moved by glaciers. Tilas was an original member of the Royal Swedish Academy of Sciences founded in 1739 and served as a president. He married Hedvig Reuterholm in 1741 and after her death in 1743, he married Anna Catharina Åkerhielm, both from influential families.

References

{{DEFAULTSORT:Tilas, Daniel 1712 births 1772 deaths 18th-century Swedish geologists Members of the Royal Swedish Academy of Sciences People from Lindesberg Municipality