Hotsonite

Hotsonite
General
Category Phosphate minerals, sulfate minerals
Formula
(repeating unit)		 Al11(PO4)2(SO4)3(OH)21.16H2O
Strunz classification 08.DF.05
Dana classification 43.05.18.01
Crystal system Triclinic
Space group 1
Unit cell a= 0.9631, b= 1.0, c= 0.9048
Identification
Color White
Crystal habit Compact
Fracture Earthy
Mohs scale hardness 2.5
Luster Silky
Streak White
Diaphaneity Transparent
Specific gravity 2.06
Density 2.060-2.068
Refractive index Less than 0.003
Other characteristics Sometimes weakly fluorescent under SW and LW UV
References [1][2][3]

Hotsonite is a mineral with the formula ([[Al<sub>11</sub>(PO<sub>4)<sub>2</sub></sub>(SO<sub>4)<sub>3</sub></sub>(OH)<sub>21</sub>.16H<sub>2</sub>O]].[4] The name derived from the farm Hotson 42, located 65 km west of the town of Pofadder, in Bushmanland, northwestern Cape Province, South Africa. This is an arid region with an average rainfall of 3 inches per annum. The name was approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association (July 1983).[4] It is chemically related to sanjuanite and kribergite.

Discovery and occurrence

Hotsonite was discovered while investigating for aluminous metamorphic rocks in an abandoned sillimanite quarry in 1982. The two senior authors sampled peculiar veins and encrustations of cryptocrystalline fine-grained white material. One of the materials had properties which could not be matched to any known mineral.

The mineral occurs closely with zaherite, Al12(SO4)5(SO4)3(OH)26.20H2O.[4]

Physical properties

Hotsonite's physical properties are similar to other hydrated aluminous sulfates and some phosphates. It occurs as a white chalk like mineral with a dull to silky luster, and an earthy fracture. When observed under magnification of 500 times, it has a flaky appearance. Hotsonite appears with a white coloration, and small grain size. The Mohs hardness is 2.5, and with a density value of 2.060 to 2.068.[4]

Chemical composition

The chemical analysis was carried out using X-ray fluorescence, and the water was calculated by the Penfield method.

[4]

Oxidewt %
SiO20.35
Al2O3 39.15
Fe2O3 0.03
MgO0.28
CaO0.24
Na2O0.21
K2O0.00
P2O5 9.85
SO3 16.80
H2O33.30
Total100.21

Diffraction information

Powder diffraction used for hotsonite data:

[4]

d(obs)d(calc)(hkl)l/l
10.0510.05010100
8.458.4211-140
6.136.110111
5.485.501111
5.205.1911-210
5.015.0302010
4.974.971-1-12
4.774.7620-12
4.634.6410-220
4.434.4322010
4.344.3421-27
3.913.910127
3.673.672-1-110
3.623.632-112
3.463.461-2-16
3.303.3122-31
3.133.1433-23
3.083.083112
2.972.9730-21
2.872.8724-12
2.832.8312-22
2.752.752221
2.682.6834-11
2.582.6022-41
2.562.5604-21
2.472.474301
2.412.414111
2.342.342411
2.322.3220-41
2.282.282-321
2.252.253441
2.232.2335-11
2.172.175111
2.142.143031
2.112.115101
2.062.0641-41
2.012.010501
1.984--1
1.944--2
1.921--1
1.900--1
1.867--1
1.844--1
1.782--3
1.687--1
1.682--1
1.665--1
1.585--2
1.539--1
1.526--1
1.495--1
1.462--1
1.449--1
1.407--1
1.378--1
1.368--1

References

  1. ↑ Beukes, Gerhard J.; Schoch, Aylva E.; Van De Westhuizen, Willem A.; Bok, Lois D. C.; De Bruiyn, Hendrik (1984). "Hotsonite,a new hydrated aluminum-phosphate-sulphate from Pofadder, South Africa" (PDF). American Mineralogist. 69: 979–983.
  2. ↑ http://webmineral.com/data/Hotsonite-VII.shtml#.WgNoImhSzIU
  3. ↑ Hotsonite on Mindat.org
  4. 1 2 3 4 5 6 Buekes, Gerhard S. (1984) http://www.minsocam.org/ammin/AM69/AM69_979.pdf title:Hotsonite, a new hydrated aluminum'phosphate-sulphate from Pofadder, South Africa
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