Properties of Vermiculite

Exfoliation or Expansion

When heated quickly to an elevated temperature, particles of vermiculite exfoliate by expanding at right angles to the cleavage, into worm-like pieces (the name vermiculite is derived from the Latin 'vermiculare', to breed worms). This characteristic of exfoliation, the basis for commercial use of the mineral, is the result of the mechanical separation of the layers by the rapid conversion of contained water to steam. The increase in bulk volume of commercial grades is 8 to 12 times, but individual flakes may exfoliate as many as 30 times. There is a color change during expansion that is dependent upon the composition of the vermiculite and furnace temperature.

Typical Physical Properties Of Exfoliated Vermiculite

Color:	Light to dark brown
Shape:	Accordion-shaped granule
Bulk density:	64 - 160 kg/cum 4 - 10 lb/cuft
Moisture loss @ 110^oC (230^oF):	4 - 10%
pH (in water):	6 - 9
Combustibility:	Non-combustible
Sintering temperature:	1150 - 1250^oC 2100 - 2280^oF
Fusion point:	1200 - 1320^oC 2200 - 2400^oF
Cation exchange capacity :	50 - 150 me/100g
Specific heat:	0.84 - 1.08 kJ/kgK 0.20 - 0.26 kcal/kgK 0.20 - 0.26 Btu/lb^oF
Waterholding capacity :	200 - 325% by wt 20 - 50% by vol

Thermal conductivity at different bulk densities

Bulk Densities		Thermal Conductivity Value
kg/cum	lb/cuft	Lambda W/mK	Btu in/sqft h^oF
56-64	3.5-4.0	0.058	0.40
80-96	5.0-6.0	0.064	0.44
160-192	10-12	0.071	0.49

Notes:

(a) Bulk density and water holding capacity vary with particle size.

(b) Exchangeable ions are Mg ^{+ 2} and Ca ^{+ 2} sodium acetate saturation/ammonium acetate substitution method.

Typical Sieve Analysis

Grading Cummulative Percent Retained U.S. Sieve No.
	3 1/2	5	7	14	25	30	50	60
Coarse (4)	35-55	60-85		90-100
Medium (4/8)		5-20	30-65	75-95	90-100
Fine (8/14)			0-10	60-85		90-100
Superfine(10/24)				10-35	60-85		90-100
Micron (20/50)					10-35		60-85	90-100

Sizes and densities of the standard grades are as follows:

Grade	Size	Density (lb/ft³)
Coarse (4)	8mm	4.7 - 6.0
Medium (4/8)	4mm	5.0 - 6.5
Fine (8/14)	2mm	5.3 - 7.0
Superfine(10/24)	1mm	5.6 - 8.0
Micron (20/60)	0.71mm	6.4 - 10.0

Packaging: Exfoliated

Approximately 4 cuft HDPE bags. Weight range of 10 to 25 kgs/bag.

Asbestos Content

A microscopical examination of vermiculite from the Palabora Mining Company Limited deposit has shown that no asbestos is present in it.

Free Silica Content

A laboratory examination of Palabora vermiculite gave a free silica content by chemical analysis of less than 1%.

Typical Range of Chemical Analysis
SiO₂	38.0 to 49.0 %
MgO	20.0 to 23.5%
AI₂O₃	12.0 to 17.5%
Fe₂O₃	5.4 to 9.3%
FeO	0 to 1.2%
K₂O	5.2 to 7.9%
Na₂O	0 to 0.8%
CaO	0.7 to 1.5%
TiO₂	0 to 1.5%
Cr₂O₃	0 to 0.5%
MnO	0.1 to 0.3%
CI	0 to 0.5%
CO₂	0 to 0.6%
S	0 to 0.2%
H₂O	5.2 to 11.5%

Specific Heat 0.2
Specific Gravity 2.6
pH value 8.0 but due to the presence of associated alkaline impurities the reaction is normally alkaline
Thermal conductivity k = 0.43 - 0.45 Btu in/ft² h ^oF
Vermiculite is incombustible
Vermiculite is inert to organic solvents, and is insoluble in water
Vermiculite is clean to handle, non-abrasive, reflective, rot proof, odorless, moldable and non-irritant

Vermiculite Products

(Draft - Under Construction)