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By careful experiments, Gadolin determined that approximately 38% of the sample was a previously unknown "earth", an oxide which was later named yttria. [17] [18] Yttria, or yttrium oxide, was the first known rare-earth metal compound—at that time, it was not yet regarded as an element in the modern sense. His work was published in 1794.
The chemical elements were discovered in identified minerals and with the help of the identified elements the mineral crystal structure could be described. One milestone was the discovery of the geometrical law of crystallization by René Just Haüy , a further development of the work by Nicolas Steno and Jean-Baptiste L. Romé de l'Isle (the ...
Chrysoprase (also spelled chrysophrase) is a green variety of chalcedony, which has been colored by nickel oxide. (The darker varieties of chrysoprase are also referred to as prase. However, the term prase is also used to describe green quartz and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety.)
Gregor found an oxide of a new metal in ilmenite; Klaproth independently discovered the element in rutile in 1795 and named it. The pure metallic form was only obtained in 1910 by Matthew A. Hunter. [97] [98] 39 Yttrium: 1794 J. Gadolin: 1843 H. Rose: Johan Gadolin discovered the earth in gadolinite in 1794.
The metal to color should be completely free from oxide and grease. Protective clothing, gloves and goggles should be used in a well-ventilated area or outdoors. Black for silver . Items are immersed in a 2.5% solution of potassium or sodium sulfide, after the appearance of the color wash objects well and wax or varnish it. [26]
Wax has been used since antiquity as a temporary, removable model in lost-wax casting of gold, silver and other materials. Wax with colorful pigments added has been used as a medium in encaustic painting , and is used today in the manufacture of crayons , china markers and colored pencils .
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The earliest gold metallurgy is known from the Varna culture in Bulgaria, dating from c. 4600 BC. [6] Silver, copper, tin and meteoric iron can also be found native, allowing a limited amount of metalworking in ancient cultures. [7] Egyptian weapons made from meteoric iron in about 3000 BC were highly prized as "daggers from Heaven". [8]