Laboratory Formation of Taranakite — Liu, Sherman, and Swindale 
497 
Taranakite, or other similarly complex potassic 
alumino-phosphate minerals, appears to be the 
most likely reaction product to be identified in 
soils to which potash and phosphate fertilizers 
have been added together or over a short time 
interval. In this study a search was made for 
the presence of taranakite in a highly aluminous 
soil to which potash and phosphate fertilizers 
had been added. 
Records of naturally occurring taranakite are 
rare. Bannister and Hutchinson (1947) studied 
several native taranakite minerals, and pointed 
out that taranakite is usually found under moist 
conditions in localities where phosphate solu- 
tions from bird or bat guano react with rock or 
clay. The formula is given as 
H 6 K 3 A1 5 (P0 4 ) 9 • 8H 2 0. 
Taranakite is massive, claylike, pulverulent to 
compact; its color is white-gray or yellowish- 
white, and it is very soft and unctuous to the 
touch. This mineral was first found in 1865 on 
rocks which were being used for bird colonies 
at Sugarloaves, Taranaki, New Zealand. The 
minerals minervite (France) and palmerite 
(Italy) have been found to be identical with 
taranakite. Chemical analysis of the taranakite 
occurring at Sugarloaves, Taranaki, New Zeal- 
and (Dana, 1951), is as follows (in %): 
KoO, 4.20; CaO, 0.55; Al 2 O s , 21.43; P 2 0 5 , 
35.05; H s O, 33.06; Insol., 0.80; Cl, 0.46; 
S0 3 , trace; FeO, 4.45. 
Murray and Dietrich (1956) also reported 
the occurrence of natural taranakite in a Virginia 
cave that was the home of a colony of bats. 
The taranakite was associated with brushite, a 
calcium phosphate mineral. 
In artificial systems having soil constituents, 
crystalline phosphate products containing potas- 
sium and aluminum have been synthesized. Bir- 
rell (1961), in New Zealand, showed that the 
addition of monopotassium phosphate to allo- 
phane produces a taranakite, the X-ray diffrac- 
tion pattern of which agreed well with the 
value given by Murray and Dietrich (1956). 
Lindsay et al. (1962) synthesized taranakite 
from Hartsells soil (from Tennessee) by add- 
ing monopotassium phosphate to the soil. 
Wada (1959) reported the identification of 
taranakite-like phosphate minerals resulting 
from the reaction of monoammonium phosphate 
with allophane and halloysite. Lindsay et al. 
(1962) identified the reaction product of am- 
monium phosphate and Hartsells soil as ammo- 
nium taranakite. Tamimi et al. (1963) were 
able to identify an ammonium-taranakite by 
means of X-ray diffraction technique. The syn- 
thetic mineral was obtained from three Latosolic 
soils derived from volcanic ash — namely Akaka 
silty clay, Hilo silty clay loam, and Paauhau 
silty clay loam — by the addition of ammonium 
chloride or diammonium phosphate in the pres- 
ence of phosphoric acid. The reaction products 
were similar to the taranakite-like minerals ob- 
tained by Wada from Japanese allophane and 
halloysite. Tamimi (1964) postulated that 
taranakite could form in soils having pH values 
ranging from 1.85 to 5.55, although no tarana- 
kite was identified in soils with a pH above 3-9- 
Haseman et al. (1950) also had indicated that 
synthetic taranakite is stable at pH values of 
about 1.7-5. 3. Kittrick and Jackson (1956) 
found that taranakite can be formed at room 
temperature by the addition of molar potassium 
dihydrogen phosphate to kaolinite. Beaton et al. 
(1964) treated kaolinite with saturated, instead 
of one molar, monopotassium phosphate solu- 
tion and found no evidence of taranakite forma- 
tion. 
In addition to chemical, optical, and X-ray 
methods, Arlidge et al. (1963) found that 
infrared spectroscopy and differential thermal 
analysis were valuable complementary methods 
to X-ray studies in the identification of tarana- 
kite and compounds of similar nature. Infrared 
spectroscopy, moreover, also gave information 
on their structure and degree of crystallinity. 
MATERIALS 
The sample selected for study was a subsoil 
of an Akaka silty clay loam taken from a steep 
road bank near the beginning of the forest 
reserve area on Kaiwiki Road, approximately 5 
miles west of the main Hilo-Hamakua Highway 
on the island of Hawaii. Sampling depth was 
from 12 to 30 inches. The sample had a pH 
value of 5.5 and was a smeary clay. The soil 
was dominated by amorphous hydrous oxides 
of aluminum and iron. It also contained small 
amounts of crystalline gibbsite, goethite, mag- 
netite, mica, and quartz (Tamura et al., 1953). 
