MONTICELLITE

    Class : Silicates
    Subclass : Nesosilicates
    Crystal system : Orthorhombic
    Chemistry : CaMgSiO4
    Rarity : Rare to uncommon

Monticellite belongs to the group of olivines of which it is one of the least common representatives. It is a high temperature mineral in calcic contexts, which is mainly encountered in metamorphic impure dolomitic limestones and skarns in contact with gabbros or granites. It is rarer in certain ultrabasic rocks, nepheline basalts, carbonatites and lamprophyres. It is also found in certain meteorites. It was named in honor of the Italian mineralogist Teodoro Monticelli. Monticellite rarely appears in short prismatic crystals, frequently rounded, but they can still reach 5 cm. The color is quite bland : whitish to greenish gray or yellowish gray.

Main photo : Monticellite from Caspar quarry, Ettringen, Germany © Volker Betz

Monticellite in the World

Monticellite is known from many sites. The most beautiful crystals come from Crestmore (California), the skarn of Magnet Cove (Arkansas) and Cascade Mountain (New York). Beautiful centimeter-sized crystals, the first identified, were discovered in blocks of metamorphic limestone thrown up by Vesuvius and Mount Somma (Italy).

Right photo : Monticellite and brown vesuvianite from Crestmore, California, USA © Rob Lavinsky


Monticellite in France

Montgomeryite is not present in the French underground.

Twinning

A twin is known on {031}, forming 6-pointed stars.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 5 to 5.5
Density : 3.03 to 3.27
Fracture : Irregular to sub-conchoidal
Streak : White

TP : Opaque to transparent
RI : 1.639 to 1.680
Birefringence : 0.014 to 0.017
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None