from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A complex brownish-black mineral, UO2, forming the chief ore of uranium and containing variable amounts of radium, lead, thorium, and other elements. It is isomorphous with thorianite.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any of several brownish-black forms of uranium dioxide, UO2, (especially pitchblende) that is the chief ore of uranium; it is isomorphous with thorianite.
from the GNU version of the Collaborative International Dictionary of English
- n. A mineral consisting chiefly of uranium oxide with some lead, thorium, etc., occurring in black octahedrons, also in masses with a pitchlike luster; pitchblende.
from The Century Dictionary and Cyclopedia
- n. This mineral, in its different varieties (the crystallized kinds called cleveite, bröggerite, nivenite, etc., and the more abundant amorphous and impure pitchblende), has become of much importance as being the chief source of radium. See radium and radioactivity. From the investigation of it also has been derived a large part of our present knowledge of the transformation of uranium into radium and the further successive changes of the latter element with lead as the probable final step: all analyses have shown a small amount of this element whose presence was hitherto unexplained. It has also been found that many varieties of uraninite yield the gas helium, which is one of the early transformation products of radium.
- n. A mineral of a pitch-black color and very heavy, having when unaltered a specific gravity of 9.5.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a mineral consisting of uranium oxide and trace amounts of radium and thorium and polonium and lead and helium; uraninite in massive form is called pitchblende which is the chief uranium ore
Certain minerals, such as uraninite, cannot form under significant exposure to oxygen.
Some researchers have found that the uranium conglomerates bearing uraninite have a texture and mineralogical makeup (uraninite, pyrite, molybdenite, and sulfides) one would expect if they were deposited by hydrothermal solutions, indicating that the uranium was deposited deep in the earth, far removed from the atmosphere, similar to what is observed happening in the origin of modern and more recently formed uraninite deposits9 (which obviously occurred in an oxygenic atmosphere).
Tamzek asserts that the mineral uraninite, present on the early Earth, cannot form under “significant exposure to oxygen”, however a recent publication from the Nasa Astrobiology Institute stated that its P.I. had observed the, “survival of uraninite … under an oxic atmosphere” and instability of uraninite under an oxygen-poor atmosphere, which was said to be “supporting … evidence for … an oxic Archaean atmosphere.”
On page 17 Wells notes that uraninite deposits have been found in more recent rocks, but neglects to mention to his readers that these only occur under rapid-burial conditions, whereas ancient deposits of uraninite occur in slow deposition conditions, for example in sediments laid down by rivers, so that the minerals were exposed to atmospheric gases for significant periods of time before burial.
This led Davidson9 to conclude that the uraninite bearing rocks are not placer riverine deposits, as is suggested by Tamzek.
He already knew ore -- the glossy, sub-metallic, pitchy black luster of uraninite or pitchblende; the yellows of autunite and carnotite; the variant and confusing greens of tobernite.
Pitchblende or uraninite is an intensely black mineral of a specific gravity of 9.5 and is found in commercial quantities in
There were two other mines that produced the same uraninite ore as the one at which Hanlon was stationed.
He was standing there, to all appearances strictly on the job of making his charges work, when Philander came crawling up the rise into the pocket where this crew was mining the glossy, lustrous pitch-blank uraninite ore.
The principal sources of uranium and radium are the minerals carnotite (hydrous potassium-uranium vanadate) and pitchblende or uraninite (uranium oxide).