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Natrolite is a colourless, white, or yellow zeolite mineral consisting of sodium aluminium silicate in the form of needle-like orthorhombic crystals and a relative hardness of 6. Natrolite is most often found in cavities in basalt. It is formed through the alteration of plagioclase feldspar, nepheline or sodalite.
Natrolite was confirmed as a distinct species in 1803.
 Research Natrolite
Nepheline is a mineral that has the formulae (Na,K)AlSiO4 and a relative hardness of 6. It is formed mainly in pegmatite associated with nepheline syenite, but may also occur in gneiss and schist. Nepheline is associated with feldspars, calcite, cancrinite, hornblende and sodalite.
Research Nepheline
Phonolite or clinkstone is a volcanic rock, consisting essentially of nepheline and sanidine feldspar. It usually also contains some form of augite, hornblende or biotite.
Research Phonolite
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The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
©1993 - 2009 The Probert Encyclopaedia
Southampton, United Kingdom
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