BORN OF EARTH AND FIRE, pumice is formed during volcanic pyroclasic events, typically spewed as ash that falls and drifts into deposits or as part of a massive pyroclastic flow. Many factors affect the useful quality, color, and purity of a pumice deposit, but on a chemical analysis level, pumice is basically an aluminum silicate. With no crystalline structure, pumice is a naturally calcined amorphous glass made up of a maze of air-filled vesicles.
The word pumice is derived from the Latin word pumex, meaning foam. Deep underground, molten rock incorporates water and other gases, and when the magma erupts from a volcanic vent, the gases flash off, leaving behind a frothy, vesicle-riven structure that quickly cools, solidifying the foamy structure.
Pumice enjoys a well-deserved green cred, as it is an abundant and sustainable resource, easily mined from surface deposits, and, having been naturally calcined (super-heated) in the fiery heat of a volcano, the only refining needed is to crush and screen it to grade.
Description: Non-crystalline (amorphous) foamed glass stone of volcanic origin. Grey-white (stone grades) to white (powder grades) in appearance.
Brightness (GE): 84
Hardness (MOHS): 6
pH: 7.2 (neutral)
Reactivity: Inert (except in the presence of calcium hydroxide or hydrofluoric acid)
Loose Bulk Density: Varies with grade (Download Technical Data Sheet of specific product below)
Specific Gravity: 2.35
Softening Point: 900 Degrees C
Water Soluble Substances: 0.15%
Chemical Name: Amorphous Aluminum Silicate
Composition: Primarily made up of Silicon Dioxide and Aluminum Oxide with traces of other oxides.
Silicon Dioxide: 76.2%
Aluminum Oxide: 13.5%
Ferric Oxide: 1.1%
Ferrous Oxide: 0.1%
Sodium Oxide: 1.6%
Potassium Oxide: 1.8%
Calcium Oxide: 0.8%
Titanium Oxide: 0.2%
Magnesium Oxide: 0.05%
Crystalline SiO2:: none detected
ADDITIONAL INFORMATION and SUPPORT DOCUMENTS:
Pumice Safety Data Sheet (PDF)
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