Nesosilicate (insular SiO4 groups), humite group, forms a solid solution with manganhumite (Dana).
Specific gravity: 3.20 to 3.32
Colour: White, yellow, dark orange or brown
Solubility: Soluble in hydrochloric and sulphuric acid with the production of silica gel; gives up fluorine in concentrated sulphuric acid (Dana).
Common impurities: Ti,Al,Mn,Ca
Humite occurs in metamorphosed and metasomatised inpure limestone and
dolostone adjacent to acid and less frequently alkaline plutonic rocks, especially
where metasomatism has introduced iron, boron and fluorine
It is commonly interleaved with clinohumite
Associated minerals include grossular, wollastonite, forsterite, monticellite, cuspidine, fluoborite, ludwigite, spinel, brucite, calcite, dolomite, serpentine, diopside, corundum, phlogopite and pyrrhotite (DHZ1A, HOM)
The humite group minerals alter readily to serpentine, chlorite and calcite (DHZ1A).
The type Locality is Monte Somma, Somma-Vesuvius Complex, Naples, Campania, Italy.
At Anzahamarono, Madagascar, humite occurs in marble with spinel (Dana).
In the Glomfjord area, northern Norway, humite occurs in chondrodite - humite - spinel - brucite - calcite - pyrrhotite assemblages in marble; the chondrodite and humite are commonly interleaved and both minerals are partially replaced by brucite (DHZ1A).
At the South Harris igneous complex, Outer Hebrides, Scotland, UK, humite occurs in forsterite and diopside marble xenoliths within metamorphosed tonalite, chondrodite and humite both occur as small rounded grains along the margins of partly serpentinised crystals of forsterite (DHZ1A).
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