This tectosilicate mineral, Natrolite is part of the group “Zeolite,” that represents a Hydrated Silicate of Aluminium and Sodium, which is available in Germany. This mineral also goes under the names, Needle zeolite or Needle stone, given to it because of the acicular crystal habits that render the mineral very thin, and you find them aggregated on tofts that appear divergent. These crystals display an epitaxial overgrowth of Gonnardite, Natrolite or Mesolite.
Derivation of Name
Klaproth, Martin Heinrich named it as Natrolite in 1803. The name derives from νατρών (Natron), a Greek word meaning soda, a pointer to its sodium content. λίθος (lithos), means stone.
Natrolite appears in the amygdaloidal cavities with other zeolites of igneous, basaltic rocks. It is also widespread in the syenites (Wiki explains it as a coarse-grained intrusive igneous rock) of Nepheline.
It is occasionally used as gemstones.
Outstanding varieties of prismatic white crystals of diverging groups are located in dense basalt at the Puy-deMarman, Puy-de-Dôme, France. Huge crystals, measuring 30 cm by 13 cm have been excavated from the Kola Peninsula in Russia. In the basalt cavities of the walls of the Giants Causeway, in CountyAntrim, are often coated with slight Natrolite needles and one can find identical material in abundance in Salesel, Aussig, and several parts of northern Bohemia among the Basalt and Phonolite volcanic rocks.
Natrolite is a widespread and well-accepted zeolite mineral. Its glowing sprays of ice clear acicular crystals are not elite to Natrolite but they are characteristic of this mineral. Though Natrolite by itself is excellent, it is often an associate of other minerals, and can add to the beauty of associated minerals like Apophyllite, Benitoite, Heulandite and others. Most often, bigger crystals appear like a low pyramid terminating a square prism with an angle of almost ninety degrees. The crystals have a tetragonal appearance, though really orthorhombic. There cleavages and the faces of the prism have a perfectly parallel configuration. The mineral is also frequently found in dense fibrous aggregates, with a radial arrangement of the fibers. Natrolite is easily distinguishable from other zeolites that are fibrous due to its special optical characteristics.
Color is white or clear, also tinted yellow and brown.
Mohs scale hardness