Fiji Pink Sand

Fiji pink is a calcareous sand made of aragonite, a naturally occurring crystal form of calcium. It is intended primarily as a decorative sand for aquariums. According to its supplier, Carib Sea, Inc, Fiji pink sand contains millions of live bacteria and has surface features that contribute to its high surface area which promotes bacterial growth. The supplier advertises that the Fiji sand has a soft pink color from an undisclosed location. Fiji pink is classified as a mixture of sub-angular and sub-rounded particles, as shown in Fig. 4.133. Selected DIA images of Fiji pink are also presented in Fig. 4.134.

Grain size distributions of Fiji pink sand are presented using several size descriptors in Fig. 4.135. Fig. 4.136 also depicts variation between number and volume distribution. The size of number distribution is dominated by the finer particles while volume distribution is dominated by the larger particles. The grain size D50 of Fiji pink is 742 µm. Typical particle size diameters in µm corresponding to several particle size descriptors are presented in Table 4.90. Comparison between EQPC sizes corresponding to various particle size diameters by weight/volume and number distributions are also presented in Table 4.91.

The density distribution for a number of commonly used shape descriptors is presented in Fig. 4.137 and summarized in Table 4.92. The distribution is clearly non gaussian and is thus fit with Johnson’s parameters. The fitting parameters are summarized in Table 4.93, and the goodness of fit is depicted in Fig. 4.138.


Fig. 4.133. Photo of Fiji pink sand with a 19 mm diameter US Penny for scale.

Fig. 4.133. Photo of Fiji pink sand with a 19 mm diameter US Penny for scale.


Fig. 4.134. Images of Fiji Pink sand acquired using 2D DIA.

Fig. 4.134. Images of Fiji Pink sand acquired using 2D DIA.


Table 4.90 Typical particle size diameters in µm corresponding to several particle size descriptors (by weight/volume distribution).

Fiji pink D1 D5 D10 D30 D50 D60 D90 D99
Feret-max 191 375 518 783 978 1072 1476 2267
EQPC 147 299 408 602 742 812 1110 1684
Feret-min 130 253 331 496 624 687 1008 1458


Table 4.91 Typical EQPC corresponding to various particle size diameters by weight/volume and number distributions.

Fiji pink D1 D5 D10 D30 D50 D60 D90 D99
Volume 147 299 408 602 742 812 1110 1684
Number 3 4 4 6 8 10 32 413


Table 4.92 Statistics of particle shape descriptors for Fiji Pink sand by number and volume distributions.

Fiji pink AR S Cx Rwadell
Number
Mean 0.65 0.80 0.93 0.61
Median 0.66 0.81 0.94 0.60
Standard Deviation 0.15 0.08 0.05 0.13
Volume
Mean 0.65 0.80 0.94 0.55
Median 0.66 0.81 0.94 0.55
Standard Deviation 0.14 0.06 0.04 0.13


Table 4.93 Johnson fitting parameters for Fiji Pink sand.

Fiji pink γ δ ξ λ
AR -0.70 1.30 0.11 0.89
S 3.16 3.39 0.95 0.13
Cx -10.60 1.99 -10.48 11.48
Rwadell 0.74 2.27 0.05 1.20

Fig. 4.135. Particle size distributions using various size descriptors.

Fig. 4.135. Particle size distributions using various size descriptors.Fig. 4.136. Particle size volume and number distributions.

Fig. 4.136. Particle size volume and number distributions.Fig. 4.137. Particle shape density distributions (based on volume) for Fiji Pink sand.

Fig. 4.137. Particle shape density distributions (based on volume) for Fiji Pink sand.

Aspect Ratio - Fig. 4.138.1
Sphericity - Fig. 4.138.2
Convexity - Fig. 4.138.3
Wadell Roundness - Fig. 4.138.4

Fig. 4.138. Johnson fitting of shape descriptors for Fiji pink.