**1.6.2. Turneaureite**

difference enables chlorapatite to accept smaller cations without the distortion will not be

Svabite is rare accessory mineral in calc-silicate skarns and arsenate analogue of fluorapatite [15] with the composition given by the formula Ca10(AsO4)6F2 (calcium fluorarsenate, CAAP). The mineral was named in 1981 by SJÖGREN [159] according to the Swedish chemist ANTON VON SWAB (1703–1768), who distilled zinc from calamine (smithsonite, ZnCO3 [160]) [161]. Svabite has the same crystal habit as apatite, with rough hexagonal prisms, some of which show rounded pyramidal termination [162]. The structure of mineral svabite is shown in **Fig. 23**.

**Fig. 23.** The structure (perspective view along the *c*-axis) and examples of crystal habits of svabite.

It is brittle mineral that can be white, gray, gray-green, or colorless and transparent. The mineral is considered to be the intermediate between the apatite and the pyromorphite series. Svabite has the average density of 3.7 g·cm−3, and the hardness on the Mohs scale ranges from 4

attempted.

**1.6.1. Svabite**

**1.6. Other members of the apatite group**

36 Apatites and their Synthetic Analogues - Synthesis, Structure, Properties and Applications

**Fig. 24.** Known localities for the mineral svabite.

Turneaureite (Ca5(AsO4)3Cl, calcium chloroarsenate [7],[163]) is hexagonal mineral with the space group P63/M with following crystallographic parameters *a* = 9.81 and *c* = 6.868 Å, *a*:*c* = 1:0.700, *V* = 572.4 Å3 and *Z* = 2. The mineral is Cl analogue of svabite (**Section 1.6.1**) and OH analogue of johnbaumite (**Section 1.6.3**). The structure of turneaureite is shown in **Fig. 25**.

**Fig. 25.** The structure of turneaureite (perspective view along the *c*-axis) and examples of crystal habits of turneaureite.

The mineral occurs47 in Franklin, New Jersey; Längban, Sweden (holotype48); and Balmat, New York [164]. The name honors Dr. FREDERICK STEWART TURNEAURE, Professor Emeritus at the University of Michigan, in recognition of his contributions to the geology and mineralogy of ore deposits. The mineral occurring occasionally as colorless, slightly turbid, prismatic (only the forms {1010} and {0001} are present) crystals up to 1.5 mm long. The mineral is colorless with a vitreous to slightly greasy luster. The hardness on the Mohs scale is 5. Measured and calculated density of mineral is 3.60 and 3.63 g·cm−3, respectively [163], [164].
