What is Andesine?

It is a mineral of Silicate. By definition, Andesine must have 50 to 70 percent Sodium and 30 to 50 percent Calcium in the Sodium/Calcium crystal structure.

Andesine Chemical Formula

The chemical formula of this mineral is (Ca, Na)(Al, Si)₄O₈,where Ca/(Ca + Na) (or percent of Anorthite) is between 30 and 50%.

Andesine Form

It is mostly found in magmatic and metamorphic environment. It typically occurs in metamorphic rocks of granulite, usually showing antiperthite property. It occurs in the form of intermediate igneous rocks such as Diorite, Andesite and Syenite. This substance is also found as detrital grains in sedimentary rocks. This chemical is closely related with Quartz, Potassium Feldspar and Magnetite.

Andesine Chemical Composition

The mineral consists of Sodium (5.14%), Calcium (5.97%), Aluminum (14.06%), Silicon (27.18%) and Oxygen (47.65%). It belongs to Tectosilicates subclass and Plagioclase Feldspars group. The Plagioclase group refers to minerals that include in their chemical composition from pure Albite to pure Anorthite.

Andesine Histor

It was first found in 1841 in a mine at Marmato, Colombia. The name of this substance comes from abundance of Andesine lavas in the Andes Mountains, South America.

Picture 1 – Andesine
Source – en.wikipedia.org

Andesine Synonyms

This mineral is also known by other names such as Ab60 and An40.

Andesine Color

It can be colorless, gray, yellow-green or white in color.

Molecular Weight

Its molecular weight is 268.6 (grams per mole).

Chemical Measurement

Being a member of the plagioclase feldspar solid solution series, accurate measurement of each individual varies. Refractive indices and specific gravity of this chemical increases directly with the Calcium content.

Andesine Physical properties

Some of the physical properties of the substance are as follows:

• Density : 2.66 and 2.68. It has an average density of 2.67.
• Specific Gravity : 2.68 to 2.71.
• Hardness : On Mohs scale is 6.25.
• Transparency : It is transparent, subtransparent or translucent.
• Luster : vitreous to dull if weathered.
• Luminescence : It is non-fluorescent.
• Magnetism : Nonmagnetic in nature.
• Streak : white streak.
• Cleavage : Good cleavage.
• Fracture : It is uneven and conchoidal.
• Birefringence : 0.0085

Crystallographic Properties

It has a triclinic crystal system. Its crystal class is 1. It includes blocky or tabular crystals. Some important data about its crystal structures are as follows:

• Unit Cell Volume: 861.5 A³ (Angstorms cubed)
• Number of Molecules Per Unit Cell: 6
• Axial Ratios: a:b:c =0.6321:1:0.71
• Cell Dimensions: a = 8.155, b = 12.9, c = 9.16, Z = 6; alpha = 93.917°, beta = 116.3333°, gamma = 89.166° V = 861.52 Den(Calc)= 3.11
• X-Ray Diffraction by Intensity (I/I_o): 3.21(1), 3.18(0.9), 4.04(0.8)

The cross-section of these crystals is nearly rectangular or square with marginally slanted dome and pinacoid endings. Crystals can be usually twinned as per Albite, Baveno, Manebach and Carlsbad laws.

Calculated Data

Some of the important calculated data of this substance are as follows:

• Refraction Index: 1.545-1.562

• Electron Density: 2.65 gm/cc (Bulk Density)

• Fermion Index: 0.01

• Boson Index: 0.99

• Photoelectricity:

1. PE_Andesine = 2.27 barns/electron
2. U=PE_Andesine x rElectron Density= 6.01 barns/cc

Radioactivity

Andesine is non-radioactive.

Occurrence

This substance is found in regions like Greenland, Andes Mountains and Norway.

Andesine Use

Andesine is chiefly used as a gemstone. Earlier, this gemstone was supposed to be better when left untreated. Today, however, heat treatment is commonly used to process this material and bring out its true color. The gemstone is also used in engraving and in art works like decorative boxes.

This stone is also used in ceramic industry and in tiles, stones and bricks.

Red Andesine-Labradorite

Red Andesine-Labradorite has a rich red color and glow and commands a premium. Andesine-Labradorite is difficult to find and appears in very limited quantities.

Andesine Labradorite

The naming convention of Andesine Labradorite is disputed. It is not strictly Andesine by definition. The stone is believed to be Feldspar with composition that falls between Andesine and Labradorite in classification.

Andesine Price

Andesine is usually priced between $80 to $200 per carat, depending on color, clarity and size.

References
1. http://www.wolframalpha.com/input/?i=andesine
2. http://www.mindat.org/min-220.html
3. http://webmineral.com/data/Andesine.shtml