Nepheline

Classification：Igneous Rock

An alkaline pluton, mainly containing alkaline feldspar, nepheline and some other alkaline minerals, with low silica content and no quartz.

Nepheline a deep alkaline rock. Gray, light green, light yellow brown. Medium coarse grain. It has a granite like structure. Is mainly composed of alkali feldspar (65% ~ 70%), nepheline (15% ~ 25%) and dark alkaline minerals (10% ~ 15%). The basic feldspar is mainly feldspar, feldspar, micro plagioclase and albite, and the alkaline dark minerals are mainly aaaene pyroxene, aanite, sodium ferric amphibole, and ferric sodium amphibole. The belt structure of the pyroxene minerals is developed.

Summary：
Common magnetite, ilmenite, apatite, zircon, titanite and other accessory minerals. The main varieties are: rock clouds syenite. Is mainly composed of potassium feldspar, sodium feldspar, nepheline and lepidomelane. (2) Liu Xia syenite. (57%) is mainly composed of feldspar and nepheline (20% ~ 25%), aegirine, pyroxene, hornblende, biotite, and a small amount of sodium feldspars. (3) sodium Chardonnay syenite. Its main feature is feldspar, all of which are albite. The typical Xia sodium syenite by a plate of nepheline (15% ~ 30%), long columnar albite (50% ~ 70%) and a small amount of dark minerals. In nature, a sill, rock strain output. It is often associated with alkaline syenite, alkaline granites, alkaline gabbro and so on. Its related minerals include niobium, tantalum, rare earth, zirconium and uranium.

Brief introduction:
The most important member of the alkaline rock. In the coarse, light colored, often with light gray, green, red, yellow. First discovered in Ural, it was once described as "granite, of which quartz is replaced by fat light stone". The average rock mineral composition: 65 ~ 70% feldspar, nepheline 20%, dark minerals 10 ~ 15%. In some types, dark minerals can be up to 20 to 25%, sometimes more.
The chardonnite often forms a micrographic structure with the feldspar. Nepheline is often cancrinite, zeolite minerals, sericite, replacement. Alkaline feldspar is mainly feldspar, anorthite, micro plagioclase and albite. There are stripe feldspar. Pyroxene is mainly composed of neopite and augite, and diopside and titanaugite are rare. The pyroxene phenocryst belt is usually developed from the center to diopside, Ni Huishi and Negro. The acicular in the matrix is often acicular. Titanium pyroxene is purple, and often forms the rim of augite or diopside. Hornblende is mainly composed of sodium amphibole and iron rich amphibole, followed by amphibole and brown amphibole. The main golden brown black mica mica, periphery often grows in pyroxene and amphibole minerals. The most common accessory minerals are magnetite, ilmenite, apatite, zircon and sphene.
The common structures are like rough and similar granitic structures. There are sometimes similar flax like structures. According to mineral composition and structure characteristics, Nepheline can be divided into some varieties. Yunxia syenite, the average mineral composition: potassium feldspar 30 ~ 40%, 30 ~ 40% sodium feldspar, nepheline lepidomelane 20%, 5 ~ 10%. It has its grainy structure and resembling flax like structure. 2. The mineral composition of the stream syenite is: orthodite 57% and a few albite, nepheline 20 ~ 25%, nenite, pyroxene, hornblende 7%, and a small amount of biotite. With hypautomorphic granular structure and trachytoid structure. 3. The main characteristics of the Na Xia syenite are feldspar, all of which are all albite. The standard type of natrium alenite is composed of plate nepheline (15 ~ 30%), long columnar self shaped sodium feldspar (50 ~ 70%) and a small amount of dark minerals (agarite, iron black mica, hornblende, etc.). In addition, there are specific Nepheline sodalite syenite, cancrinite syenite, pseudoleucite syenite and syenite Feizheng. Nepheline often constitutes a single or complex rock plant. Sometimes it is an integrated intrusion in gneiss and has a gneiss like structure. Sometimes a rock, or lopolith dyke.
Nepheline is often associated with alkaline syenite and alkaline granite. Sometimes it is closely related to alkaline gabbro through alkaline two long rocks. In this case, there are occasional yellowish rocks.