THE MINERAL HUMITE

  • Chemistry: ((Mg, Fe)2SiO4)3 - Mg(F, OH)2, Magnesium Iron Silicate Fluoride Hydroxide.
  • Class: Silicates
  • Subclass: Nesosilicates
  • Group: Humite
  • Uses: Only as mineral specimens.
  • Specimens


Humite is the namesake member of the Humite Group of minerals. Members of the Humite Group are noted for having a mixture of silicate layers and oxide layers in their structures. The silicate layers have the same structure as olivine. The oxide layers have the same structure as brucite. In the case of humite, there are three consecutive olivine layers that alternate between each brucite layer. The most common member of the Humite Group is chondrodite which has only two olivine layers between each brucite layer. Humite is a fairly rare mineral. It is found in hydrothermal veins and contact and regionally metamorphosed dolomitic limestones as small prismatic crystals.

PHYSICAL CHARACTERISTICS:

  • Color is commonly yellow, but also white, brown or orange.
  • Luster is vitreous.
  • Transparency: Crystals are translucent.
  • Crystal System: Orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include small prismatic to rounded crystals, but as is most commonly the case, as embedded grains.
  • Cleavage is poor in one direction, basal.
  • Fracture is subconchoidal.
  • Hardness is 6.
  • Specific Gravity is 3.2 - 3.3
  • Streak is white.
  • Associated Minerals include magnetite, diopside, spinel, biotite, serpentine, chondrodite, olivine and calcite.
  • Notable Occurrences are include Monte Somma, Mount Vesuvius, Italy; Paragas, Finland; Varmland, Sweden; Tilly Foster Mine, Brewster, New York, USA and some other localities.
  • Best Field Indicators are color, associations, environment of formation and hardness.
HUMITE specimens:
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HUMITE specimen hum-1
$ 38.00
Dims: 1.9 x 1.8 x 1.2" (4.7 x 4.5 x 3.0 cm)
Wt: 2.5 oz. (71 g)
Cava Novella, Vesuvio, Napoli, Italy
I am relatively sure that this hand specimen is composed entirely of compact granular and crystalline Humite. Most of the material is granular, showing no crystalline form, but there are pockets that contain small white or brown crystals that show reasonably good orthorhombic crystals. These have a rather bright, vitreous luster, whereas the granular material is generally somewhat duller. The crystals also show considerable translucence and even transparence, whereas the massive material is opaque.
no photo
hum-1 ($ 38.00)
Cava Novella, Vesuvio, Napoli, Italy

 


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