lamprophyre

[lam-pruh-fahyuhr]
noun Petrology.
any dark intrusive rock in which dark minerals occur both as phenocrysts and as groundmass.

Origin:
1885–90; lampro- (< Greek lamprós clear) + -phyre

lamprophyric [lam-pruh-fir-ik] , adjective
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World English Dictionary
lamprophyre (ˈlæmprəˌfaɪə)
 
n
any of a group of basic igneous rocks consisting of feldspathoids and ferromagnesian minerals, esp biotite: occurring as dykes and minor intrusions
 
[C19: from Greek lampros bright + -phyre, from porphyry]

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American Heritage
Science Dictionary
lamprophyre   (lām'prə-fīr')  Pronunciation Key 
A dark igneous rock, having a porphyritic texture in which both the phenocrysts (larger crystals) and the matrix consist primarily of pyroxene, hornblende, and biotite.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

lamprophyre

any of a group of dark gray to black intrusive igneous rocks that generally occur as dikes (tabular bodies inserted in fissures). Such rocks are characterized by a porphyritic texture in which large crystals (phenocrysts) of dark, iron-magnesium (mafic) minerals are enclosed in a fine-grained to dense matrix (groundmass). The abundance, large size, well-formed crystal outline, and brilliantly reflecting cleavage faces of the mafic phenocrysts give the rock a striking appearance. Mafic minerals, including biotite, hornblende, augite, or olivine, not only constitute virtually all of the phenocrysts but occur in the groundmass as well, together with much potash feldspar, plagioclase, or feldspathoid.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Magnesium content in dolomitic rocks and lamprophyre dikes follows a similar pattern.
Bedrock is brecciated and fractured along contacts with lamprophyre dikes.
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