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Navajo Pumice

Oxide Analysis Formula
CaO 0.44% 0.06
K2O 5.50% 0.48
MgO 0.17% 0.03
Al2O3 12.52% 1.00
SiO2 74.20% 10.06
Fe2O3 1.62% 0.08
Oxide Weight 769.48
Formula Weight 769.48


pH (10% aqueous solution): 8.2
Hardness (Moh): 5.5-6.0
Index of Refraction: 1.5
Crushing Strength (lbs/sq in, one inch compaction): 990
Thermal Conductivity (K factor in BTU/hr/sq ft & 1 degree F/in): .63-.44
KNaO: 11.05

Formed by the tremendous pressure and heat of past geophysical activity, pumice is a natural compound of volcanic origin with practically limitless use in application extending from paint and chemical formulation to the cleaning of solid state electronic circuitry.

Navajo pumice, derived from deep, thick-bed deposits in New Mexico, is of the finest quality available. After removal from its bed, Navajo pumice is carefull selected to be free of impurities and mineral color stains. It is carefully ground to a near-white powder, analyzed and graded to meet a wide varity of uses.

When crushed it fractures into angular shapes with sharp cutting edges. When used as an abrasive it continues to fracture in use, thus constantly presenting new sharp edges to the work.

It is chemically inert and fire resistant and is an excellent additive for paints and other protective coatings. It can be used as a filtration media for chemical carrier. It is used in hand soaps and cleaners, glass cleaners, tooth polishes, facial scrubs, erasers, and in pottery as a filler and source of fluxing oxides.

It mixes and bonds well with a variety of materials, can be used as a soil substitute, filler, for compounding, and as a mold release agent.

Particle Size (US Standard Sieves):

Grade FFFF FFF FF F 0 0 1/2 0 3/4

80# 0.8 1.7 2.5
100# 1.6 1.4 3.8
120# 6.4 3.1 13.4
140# 0.6 11.9 25.6 18.5
170# 2.0 1.3 8.6 20.1 20.1
200# T T 3.0 6.7 7.4 18.0 13.8
325# 16.0 20.4 23.0 21.7 18.4 21.8 15.3

Density 48 47 45 45 44 37 36

Coarser grades are also available.

American Pumice Co, Box 4305, Santa Fe, NM 87502 505-471-9132

Related Information


Articles Volcanic Ash
Joseph Herbert overviews the technical and practical aspects of this interesting group of materials
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Materials Volcanic Ash
Typecodes Flux Source
Materials that source Na2O, K2O, Li2O, CaO, MgO and other fluxes but are not feldspars or frits. Remember that materials can be flux sources but also perform many other roles. For example, talc is a flux in high temperature glazes, but a matting agent in low temperatures ones. It can also be a flux, a filler and an expansion increaser in bodies.

By Tony Hansen

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