Joel D. Grice Robert A. Gault A.J. Criddle Richard C. Erd Andrew C. Roberts 1996 <p>Hanawaltite, ideally Hg<span style="font-size: 11.6667px;">1+</span>_{<span class="sub">6</span>}Hg^{<span class="sup">2+</span>}O_{<span class="sub">3</span>}Cl_{<span class="sub">2</span>}, is orthorhombic,&nbsp;<i><span class="italic">Pbma</span></i>&nbsp;(57), with unit-cell parameters refined from powder data:&nbsp;<i><span class="italic">a</span></i>=11.790(3),&nbsp;<i><span class="italic">b</span></i>=13.881(4),&nbsp;<i><span class="italic">c</span></i>=6.450(2) Å,&nbsp;<i><span class="italic">V</span></i>=1055.7(6) Å^{<span class="sup">3</span>},&nbsp;<i><span class="italic">a</span></i>:<i><span class="italic">b</span></i>:<i><span class="italic">c</span>&nbsp;</i>=0.8494:1:0.4647,&nbsp;<i><span class="italic">Z</span></i>=4. The strongest six lines of the X-ray powder-diffraction pattern [<i><span class="italic">d</span></i>&nbsp;in Å (<i><span class="italic">I</span></i>)(<i><span class="italic">hkl</span></i>)] are: 5.25 (80)(111), 3.164 (60)(231), 3.053 (100)(041), 2.954 (70)(141), 2.681 (50)(401), and 2.411 (50)(232,341). The mineral is an extremely rare constituent in a small prospect pit near the long-abandoned Clear Creek mercury mine, New Idria district, San Benito County, California. It was found on a single-fracture surface where it is intimately associated with calomel, native mercury, cinnabar, montroydite, and quartz. Individual crystals are subhedral to anhedral, platy to somewhat bladed, and average about 50 μm in longest dimension. The largest known crystal is approximately 0.3×0.3 mm in size and is striated parallel [001]. Hanawaltite is opaque to translucent (on very thin edges), black to very dark brown–black in color, with a black to dark red–brown streak. Other physical properties include: metallic luster; cleavage {001} good; uneven fracture; brittle; nonfluorescent;&nbsp;<i><span class="italic">H</span></i>&lt;5; calculated density (for the empirical formula) 9.51 g/cm<i><span class="sup">3</span></i>.</p><p>In polished section, hanawaltite is moderately to strongly bireflectant and is pleochroic white (<i><span class="italic">R</span></i>_{<span class="sub"><span class="italic">I</span></span>}) to blue–white (<i><span class="italic">R</span></i>_{<span class="sub">2</span>}). In reflected plane-polarized light, it is white with orange–red internal reflections in very thin grains and at grain margins. The anisotropy is strong with bright metallic blue rotation tints. Measured reflectance values, in air and in oil, are tabulated. Electron-microprobe analysis yielded Hg_{<span class="sub">2</span>}O 82.46, HgO 14.27, Cl 3.33, H_{<span class="sub">2</span>}O [0.34], sum [100.40], less O=Cl 0.75, total [99.65] wt. %, corresponding to Hg^{<span class="sup">1+</span>}_{<span class="sub">6.00</span>}Hg^{<span class="sup">2+</span>}_{<span class="sub">1.00</span>}<span>&nbsp;</span>[Cl_{<span class="sub">1.43</span>}(OH)_{<span class="sub">0.57</span>}]_{<span class="sub">Σ2.00</span>}O_{<span class="sub">3.00</span>}, based on O+Cl=5. After the crystal structure was determined, the original microprobe value for Hg_{<span class="sub">2</span>}O, 96.2, was partitioned in a ratio of 6Hg_{<span class="sub">2</span>}O:HgO and (OH) was calculated, such that Cl+(OH)=2. The hanawaltite structure consists of undulatory [Hg–Hg]^{<span class="sup">2+</span>}<span>&nbsp;</span>ribbons which roughly parallel (100). The diatomic [Hg–Hg]^{<span class="sup">2+</span>}<span>&nbsp;</span>groups have anion tails which, in turn, serve as cross linkages between dimer ribbons through [Hg^{<span class="sup">2+</span>}O_{<span class="sub">2</span>}Cl_{<span class="sub">2</span>}] planar rhombs. The structure is compared to that of other mercury oxychlorides and each is found to have its own unique structural features. This structural diversity is attributed to the inherent ability of mercury to adopt either metallic or ionic types of bonds. The mineral name honors the late Dr. J. D. (Don) Hanawalt (1903–1987), who was a pioneer in the field of X-ray powder diffraction.</p> application/pdf 10.1017/S0885715600008915 en Cambridge University Press Hanawaltite, Hg1+6Hg2+[Cl,(OH)]2O3 - A new mineral from the Clear Creek claim, San Benito County, California: Description and crystal structure article