**1.6.3. Johnbaumite**

Johnbaumite (Ca5(AsO4)3OH [165],[166]) is a hexagonal mineral from the Franklin mine from Franklin, Sussex County, New Jersey, in 1944. The mineral is arsenate analogue of hydroxy‐ lapatite and hydroxyl analogue of svabite (**Section 1.6.1**). Johnbaumite was named in 1980 according to BAUM [164]. The structure and crystal habits of johnbaumite is shown in **Fig. 26**.

<sup>47</sup> Turneaureite was found at three localities, but only the sample from Längban, Varmland, Sweden, provided single crystals of a size and quality adequate for the characterization of the specie [163].

<sup>48</sup> Holotype is the definition for single specimen (designated by the author) from which all the data from the original description were obtained. If the portion of such a specimen was send to other museum for preservation, the author shall designate this portion as "part of holotype." Other types of specimen are the cotype and the neotype. The cotype is a specimen used to obtain quantitative data for the original description (specimen examined only visually should not be considered a cotype). The neotype is a specimen chosen by author for a redefinition or reexamination of a species to represent the species when the holotype or cotypes cannot be found [5].

**Fig. 26.** The structure (perspective view along the *c*-axis) and the crystal habit of johnbaumite (a) and johnbaumite–M (b).

The space group of johnbaumite is P63/M or P63 with *a* = 9.70 Å and *c* = 6.93 Å, *a*:*c* = 1:0.714, *V* = 564.96 Å3 and *Z* = 2. Johnbaumite occurs as massive anhedral grayish-white granular material with individual grains of approximately 8 mm or less in diameter and is white to colorless with vitreous luster. Johnbaumite is colorless in thin section and has white streaks. The Mohs hardness is approximately 4½. The luster is vitreous on cleavage surfaces and slightly adamantine to greasy on fracture surfaces. The cleavage is distinct, parallel to {100}. Measured and calculated density of mineral is 3.68 and 3.73 g·cm−3, respectively. Johnbaumite is fluorescent in short-wave UV radiation with a medium pinkish orange response color [165].

The monoclinic variant of mineral, which was previously named strontiumarsenapatit and fermorite (3[(Ca,Sr)3(P,As)2O8]·Ca(OH,F)2 [74],[167], is now named johnbaumite–M and is not considered a distinct species [45]. The mineral crystallizes in the space group P21/M with crystallographic parameters *a* = 9.594 Å, *b* = 6.975 Å and *c* = 9.579 Å; *α* = *γ* = 90° and *β* = 119.97°; *V* = 556.341 Å3 ; and *Z* = 2.

#### **1.6.4. Pyromorphite**

Pyromorphite (lead chlorophosphate, Pb5(PO4)3Cl [52],[168],[169],[170],[171],[172],[188], **Fig. 27**) was named by F.L. HAUSMANN in 1813. The name was derived from Greek words for "fire" and "form" to describe the recrystallization of a mineral from the melt. The structure and the example of shape of pyromorphite are shown in **Fig. 28**. Since the structures of vanadinite and pyromorphite are similar except for the tetrahedrally coordinated cations, it is described in **Section 1.6.8**.

**Fig. 27.** Pyromorphite: (a) Brandy Gill Mine, Great Britain and (b) Friedrichsegen Mine, Bad Ems, Nassau, Germany.

**Fig. 28.** The structure of pyromorphite mineral (perspective view according to the *c*-axis) (a) and the shape of crystal from Beaujeu (b): c (0001), m (101 ¯ 0) and x (101 ¯ 1).

Lead bearing minerals pyromorphite, mimetite (**Section 1.6.7**) and vanadinite (**Section 1.6.8**) occur independently or in great variety of isomorphous mixtures. All these species were prepared synthetically and pyromorphite is also known as a furnace product in slag [173], [174].

Pyromorphite is brittle hexagonal mineral that crystallizes in the space group **P63/M** with the crystallographic parameters *a* = 9.9764, *c* = 7.3511 Å, *a*:*c* = 1:0.737, *V* = 634.14 Å3 and *Z* = 2. The mineral has the hardness from 3½ to 4 (Mohs scale) and shows the density in the range from 6.5 to 7.1 g·cm−3. The luster is resinous and the color of mineral is commonly green, varying from grass green to the lighter and darker shades. It may be also pale brown. The secondary mineral formed together with limonite, cerussite (PbCO3 [175]), hemimorphite (Zn4Si2O7(OH)2·H2O [176],[177]) and smithsonite [160] in the upper oxidized portion of lea veins [178].
