William B. Simmons

Cooling rates and crystallization dynamics of shallow level pegmatite-aplite dikes, San Diego County, California

The George Ashley Block (GAB) is a rockslide block located in the Pala pegmatite district of Southern California. It is layered, asymmetric, pocket containing, and peraluminous. The GAB consists of quartz (42 vol%), Na-rich plagioclase (27%), potassium feldspar (24%), muscovite (7%), Mn-rich garnet (2%), biotite (1%), and a trace of tourmaline and gahnite. It contains only small amounts of the incompatible elements that characterize differentiated pegmatite bodies. P2O5, MnO, and F are present in amounts of <1 wt% each; B, Be, Ce, Li, Nb, Nd, and Th are <100 ppm each. More than 90% of the garnet grains in the GAB are zoned toward Mn-rich rims, and a symmetrical change in garnet-core composition occurs across the body. The mean X site contents for garnet (in at%) are 57% Fe, 40% Mn, 3.1% Mg, and 0.4% Ca. The Mn contents of garnet range from 30 to 55 at%; Fe contents vary inversely with Mn and range from about 66 to 43 at%. It is concluded that the bulk chemistry yields little information about fractionation, but the garnet, muscovite, and biotite mineral chemistry is more useful. There may have been two separate injections of magma to form the GAB. *E-mail: wkleck@lightspeed.net †Deceased: January 8, 1998. 0003-004X/99/0506–0695

Amorphization of graphite induced by mechanical milling and subsequent crystallization of the amorphous carbon upon heat treating

05.00 695 American Mineralogist, Volume 84, pages 695–707, 1999 FIGURE 1. Location map for the George Ashley Block pegmatite. KLECK AND FOORD: GAB PEGMATITE 696 tain” was used by Jahns and Wright (1951), but the name “Heriot Mountain” appears on the most recent Pechanga Quadrangle for the same geographic feature. This area is within the Pala pegmatite district, San Diego Co., California. The Pala Indian Tribe now controls most of Heriot Mountain and is acquiring (or has acquired) the George Ashley property. At present, access has been closed to these tribal properties. Preliminary, bulk-chemical compositions and a description of some line-rock features of the GAB were published by Webber et al. (1997). Kleck (1994, 1996) presented a brief description of the GAB and some preliminary chemical data. Simpson (1965) reported one analysis and a composition computed from modal mineralogy for pegmatites in the Ramona pegmatite district. Jahns and Tuttle (1963) presented normative mineralogy (but not the actual oxide analyses) for the Katerina dike, Pala district, California; Himalaya dike, Mesa Grande district, California; and the Upper Mack dike, Rincon district, California. Jahns and Tuttle (1963) also described some of the structures in the pegmatite bodies of Southern California pegmatite districts. Jahns and Wright (1951) described the Pala pegmatite district (which includes Heriot Mountain) and provided a basic description of many pegmatite bodies in this district. That work emphasized structures, petrology, and mineralogy; no analyses of the rocks and no systematic chemistry of the minerals were reported. Analyses of minerals from Southern California pegmatite bodies (mainly pocket minerals) were reported in several publications; representative references can be found in Jahns (1955) and in Foord et al. (1989).

Proposed nomenclature for samarskite-group minerals: New data on ishikawaite and calciosamarskite

The effects of mechanical milling (MM) on the phase transformation of graphite carbon were investigated using high resolution electron microscopy (HREM), x-ray diffraction, and differential thermal analysis (DTA). Amorphization of graphite as a result of prolonged high-energy ball milling was directly observed with HREM. The exothermic peak in the DTA trace of the {approximately}200 h ball milled sample indicated a crystallization onset temperature of about 670{degree}C and crystallization activation energy of 234 kJ/mole. {copyright} {ital 1996 Materials Research Society.}

PEZZOTTAITE FROM AMBATOVITA, MADAGASCAR: A NEW GEM MINERAL

Abstract The current definition of samarskite-group minerals suggests that ishikawaite is a uranium rich variety of samarskite whereas calciosamarskite is a calcium rich variety of samarskite. Because these minerals are chemically complex, usually completely metamict, and pervasively altered, their crystal chemistry and structure are poorly understood. Warner and Ewing (1993) proposed that samarskite is an A3+B5+O4 mineral with an atomic arrangement related to α-PbO2. X-ray diffraction analyses of the recrystallized type specimen of ishikawaite and the Ca-rich samarskite reveal that they have the same structure as samarskite-(Y) recrystallized at high temperatures. Electron microprobe analyses show that the only significant difference between samarskite-(Y), ishikawaite, and calciosamarskite lies in the occupancy of the A-site. The A-site of samarskite-(Y) is dominated by Y+REE whereas the A-site of ishikawaite is dominantly U+Th and calciosamarskite is dominantly Ca. Additionally, a comparison of these data to those of Warner and Ewing (1993) show that in several cases Fe2+ or Fe3+ are dominant in the A-site. We propose that the name samarskite-(REE+Y) should be used when one of these elements is dominant and that the mineral be named with the most abundant of these elements as a suffix. The name ishikawaite should be used only when U+Th are dominant and the name calciosamarskite should only be used when Ca is the dominant cation at the A-site. Finally, because of the inability to quantify the valence state of iron in these minerals, the exact nature of the valence state of iron in these minerals could not be determined in this study.

Effects of Caffeine on the Bones of Aged, Ovariectomized Rats

Pezzottaite, ideally Cs(Be_2Li)Al_2Si_6O_(18), is a new gem mineral that is the Cs,Li–rich member of the beryl group. It was discovered in November 2002 in a granitic pegmatite near Ambatovita in central Madagascar. Only a few dozen kilograms of gem rough were mined, and the deposit appears nearly exhausted. The limited number of transparent faceted stones and cat’s-eye cabochons that have been cut usually show a deep purplish pink color. Pezzottaite is distinguished from beryl by its higher refractive indices (typically n_o=1.615–1.619 and n_e=1.607–1.610) and specific gravity values (typically 3.09–3.11). In addition, the new mineral’s infrared and Raman spectra, as well as its X-ray diffraction pattern, are distinctive, while the visible spectrum recorded with the spectrophotometer is similar to that of morganite. The color is probably caused by radiation-induced color centers involving Mn^(3+).

Liddicoatite Tourmaline From Anjanabonoina, Madagascar

Caffeine is a substance which many people consume in their daily life. Caffeine’s effects on bone are still controversial. Using ovariectomized rats, the present study was conducted to determine to what extent caffeine intake affects the mechanical properties, bone minerals and histology. Aged rats were divided into 2 groups after ovariectomy. Group 1 was fed a 20% protein diet as a control, and group 2 was fed a 20% protein diet supplemented with caffeine (2 mg/100 g body weight). The respective diets were fed to the rats of each group for 90 days. Rats were then killed by heart puncture, blood was collected, and femurs were removed. In 1 group of femurs paraffin cross-sections were made at the midshaft of each bone. Total width, cortical width, total cross-sectional bone area of the midshaft, and the number of osteocytes in randomly selected areas were measured. Another group of bones was subjected to three-point bending testing until failure. Bones were then pulverized and Ca, P, Mg, Zn, Sr, Si, hydroxyproline and hexosamine contents and crystallite size were measured. Various mechanical properties, except modulus of elasticity, in the caffeine group were consistently 7–23% lower than the noncaffeine controls. Yield strain in the caffeine group was significantly less than in the noncaffeine controls. Zinc, Sr, and crystallite size of bone showed a significant decrease in the caffeine group, whereas Si contents significantly increased. Our current results indicate that routine intake of caffeine in the elderly should be regarded with some caution.

Copper-bearing (Paraíba-type) tourmaline from Mozambique

28 LIDDICOATITE FROM MADAGASCAR GEMS & GEMOLOGY SPRING 2002 three lithium tourmalines with the general formula (Ca,Na,K, )(Li,Al)3Al6Si6O18(BO3)3(OH)3(OH,F), which are defined on the basis of their X-site occupancy: Ca = liddicoatite, Na = elbaite, and a vacant ( ) X site = rossmanite. Elbaite is the most abundant gem tourmaline, whereas rossmanite has so far been identified from few localities (Johnson and Koivula, 1998b; Selway et al., 1998), and typically is not of gem quality. However, neither can be separated from liddicoatite without quantitative chemical analysis. Therefore, in this article we use the group name tourmaline to refer to material that has not been chemically analyzed. Although liddicoatite is well characterized mineralogically, little has been published about the history, sources, and gemology of this tourmaline species in particular. This article focuses on liddicoatite from Madagascar—which is the principal historic source— and in particular on the Anjanabonoina pegmatite, By Dona M. Dirlam, Brendan M. Laurs, Federico Pezzotta, and William B. (Skip) Simmons

Falsterite, Ca2MgMn2+2(Fe2+0.5Fe3+0.5)4Zn4(PO4)8(OH)4(H2O)14, a new secondary phosphate mineral from the Palermo No. 1 pegmatite, North Groton, New Hampshire

Copper-bearing tourmaline from Mozambique was first recovered in 2001, but its Cu content was not recognized until 2003, and it was not widely sold with its Mozambique origin disclosed until 2005. It has been mined from alluvial deposits in an approximately 3 km2 area near Mavuco in the eastern portion of the Alto Ligonha pegmatite district. Most of the production has come from artisanal mining, with hand tools used to remove up to 5 m of overburden to reach the tourmaline-bearing layer. The stones exhibit a wide range of colors, typically pink to purple, violet to blue, and blue to green or yellowish green. Heat treatment of all but the green to yellowish green stones typically produces Paraiba-like blue-to-green hues by reducing absorption at ∼520 nm caused by the presence of Mn3+. The gemological properties are typical for Cu-bearing tourmaline (including material from Brazil and Nigeria); the most common inclusions consist of partially healed fractures and elongate hollow tubes. With the exception of some green to yellow-green stones, the tourmalines examined have relatively low Cu contents and very low amounts of Fe and Ti. Mechanized mining is expected to increase production from this region in the near future.

The effect of prenatal caffeine exposure on the enamel surface of the first molars of newborn rats

Abstract Falsterite, ideally Ca2MgMn2+2(Fe20.5Fe3+0.5)4Zn4(PO4)8(OH)4(H2O)14, is a new mineral from the Palermo No. 1 pegmatite in North Groton, Grafton County, New Hampshire, U.S.A., and also occurs at the Estes pegmatite quarry, Baldwin, Cumberland County, Maine, U.S.A. It formed as the result of secondary alteration of primary triphylite and associated sphalerite. The crystals occur as very thin greenish-blue plates and rectangular laths, up to 0.7 mm in length, but no more than a few micrometers thick. Laths are flattened on {010}, elongate along [100], and exhibit lamellar twinning. The mineral is transparent and has a very pale greenish-blue streak, vitreous luster, Mohs hardness of about 2, flexible tenacity, irregular fracture, and perfect cleavage on {010}. The measured and calculated densities are 2.78(3) and 2.837 g/cm3, respectively. It is optically biaxial (-), a = 1.575(10), b = 1.600(5), g = 1.610(5) (white light), 2Vmeas = 60(10), and 2Vcalc = 63.8. Falsterite exhibits strong dispersion, r > v. The optical orientation is X = b, Y ≈ a, Z ≈ c. Pleochroism is pronounced: X, Z = colorless to very pale yellow, Y = blue green; Y >> X ≈ Z. Electron-microprobe analyses (average of 7), with FeO and Fe2O3 apportioned and H2O calculated on structural grounds, provided: CaO 6.36, MgO 2.13, MnO 8.10, ZnO 18.49, FeO 8.02, Fe2O3 8.90, Al2O3 0.02, P2O5 31.81, H2O 16.17, total 100.00 wt%. The empirical formula (based on 50 O atoms) is Ca2.02Mg0.94Mn2+2.04Fe2+1.99Fe2+1.99Zn4.05P7.99O32(OH)4(H2O)14. The mineral dissolves very easily in cold, dilute HCl. Falsterite is monoclinic, P21/c, with the unit-cell parameters: a = 6.3868(18), b = 21.260(7), c = 15.365(5) Å, b = 90.564(6), V = 2086.2(1.1) Å3, and Z = 2. The eight strongest lines in the X-ray powder diffraction pattern are [dobs in Å(I)(hkl)]: 12.86(34)(011); 10.675(100)(020); 4.834(12)(102,112); 4.043(18)(132); 3.220(25)(152); 3.107(14)(044); 2.846(19)(222); 1.596(14)(0·12·4). The structure of falsterite (R1 = 6.42% for 714 Fo > 4σF) contains edge-sharing chains of Fe2+/Fe3+O6 octahedra and corner-sharing chains of ZnO4 tetrahedra along [100]. These chains are linked to one another by PO4 tetrahedra, forming a sheet parallel to {010}. Mn2+O6 octahedra and CaO7 polyhedra also link to this sheet, resulting in a thick slab. The slabs are bridged in the [010] direction by edge-sharing dimers of MgO6 octahedra, which link to the slabs by sharing edges with ZnO4 tetrahedra in adjacent slabs. The structures of falsterite and schoonerite, while topologically quite different, share similar components and structural features.

Physical examination of caffeine's effects on the enamel surface of first molar in new-born rats

Timed-pregnant rats were randomly divided into three groups at day 7 of gestation. A caffeine tablet was implanted subcutaneously in the experimental group and a placebo tablet in the control group. The third group was used as surrogate dams. At birth, eight randomly selected pups born either to the experimental or control dams were placed with surrogate dams that had produced pups on the same day; these were then used in either the experimental or the control group, and so the surrogate dams raised pups that came from either the experimental or control group. At day 22 after birth, the pups were killed, and their first and second maxillary and mandibular molars were removed. They were then placed in a specially designed chamber and exposed to an acid solution. The outflowing acid solution was collected every 20 min and up to 80 min. Then the calcium, phosphorus, and magnesium contents of each fraction were measured. The enamel surfaces of untreated and acid-treated first molars of the caffeine and control groups were examined by scanning electron microscopy. Untreated teeth were powdered and separated into enamel and dentine. Pure enamel samples were examined with a Gandolfi X-ray powder camera to measure the crystallite size. At 20-, 40- and 60-min intervals, calcium and phosphorus contents of the first molars of the caffeine group were significantly higher than those of the control. The enamel surface of the untreated and acid-treated first molars of the caffeine group had significantly different scanning microscopic appearances from those of the non-caffeine untreated and acid-treated control groups.(ABSTRACT TRUNCATED AT 250 WORDS)