FOR MANY YEARS collectors have recovered microcline and albite (variety cleavelandite) specimens from various localities within the Pikes Peak batholith that had unusual irregular hexagonal holes. ...

John Meeks Shannon, museum director, historian, and longtime fixture in the Denver and Tucson mineral shows, passed away in Lakewood, Colorado, on 4 March 2015. He was born in Pampa, Texas, to Cleo...

Geodes containing celestine with associated quartz, calcite, chlorite, and other minerals occur in the Jurassic Curtis Formation of Emery and Wayne counties off the east and south flanks of the San...

Other| May 01, 2009 Memorial of Benjamin F. Leonard III, 1921–2008 Daniel E. Kile; Daniel E. Kile * 1U.S. Geological Survey, MS 413, Denver Federal Center, Denver, Colorado 80225, U.S.A. *E-mails: dekile@usgs.gov; kvevans@usgs.gov Search for other works by this author on: GSW Google Scholar Karl V. Evans Karl V. Evans * 2U.S. Geological Survey, MS 973, Denver Federal Center, Denver, Colorado 80225, U.S.A. *E-mails: dekile@usgs.gov; kvevans@usgs.gov Search for other works by this author on: GSW Google Scholar Author and Article Information Daniel E. Kile * 1U.S. Geological Survey, MS 413, Denver Federal Center, Denver, Colorado 80225, U.S.A. Karl V. Evans * 2U.S. Geological Survey, MS 973, Denver Federal Center, Denver, Colorado 80225, U.S.A. *E-mails: dekile@usgs.gov; kvevans@usgs.gov Publisher: Mineralogical Society of America First Online: 02 Mar 2017 Online ISSN: 1945-3027 Print ISSN: 0003-004X © 2009 American Mineralogist American Mineralogist (2009) 94 (5-6): 859–861. https://doi.org/10.2138/am.2009.545 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Daniel E. Kile, Karl V. Evans; Memorial of Benjamin F. Leonard III, 1921–2008. American Mineralogist 2009;; 94 (5-6): 859–861. doi: https://doi.org/10.2138/am.2009.545 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Benjamin Franklin Leonard III, at age 87, passed away peacefully at his home in McCall, Idaho, on September 5, 2008. Ben had a long and distinguished career at the U.S. Geological Survey, where he established himself as an accomplished field geologist and an internationally recognized expert in ore microscopy. Born in Dobbs Ferry, New York, on May 12, 1921, Ben spent much of his early life in the eastern United States, graduating from Hamilton College in 1942 (B.S.), a salutatorian and member of Phi Beta Kappa, and then Princeton University in 1946 (M.A.) and 1951 (Ph.D.), where he was a... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Des echantillons provenant de 105 cavites dans des filons de pegmatite miarolitique granitique de part et d'autre du batholite de Pikes Peak, au Colorado, ont ete analyses par diffraction X (methode des poudres). Smectite (beidellite), illite, et kaolinite sont presentes dans ces cavites. Un calcul de la distribution de l'epaisseur des cristallites, de leur epaisseur moyenne, et de la variance de leur epaisseur permet de determiner la provenance et le mode de formation de l'illite et de la smectite. L'illite et la smectite authigenes des cavites miarolitiques font preuve d'une distribution log-normale de l'epaisseur des cristallites, et une epaisseur superieure par rapport a leur homologues derives des sols; l'illite des cavites ayant une distribution non log-normale des epaisseurs resulterait d'un melange d'illite formee dans la cavite et d'illite derivee de sols. Une analyse des epaisseurs moyennes et de la variance des epaisseurs montre que la croissance de l'illite a ete initiee par un evenement bref causant la nucleation, suivi d'un episode ou la cinetique etait regie par les surfaces. La cristallisation des argiles dans les cavites miarolitiques resulterait d'une neoformation aux depens d'une phase fluide hydrothermale. L'evaluation de provenance permet une determination des distributions regionale et locale des mineraux argileux dans les cavites miarolitiques au sein du batholite de Pikes Peak.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

eolites, the theme of the Denver 2004 Gem and Mineral Show, are well represented in Colorado. In particular, the Table Mountains near Golden have been known as a source of excellent specimen-quality zeolites and associated minerals for more than 115 years. Although overshadowed in recent years by the tremendous quantity of material from India, this classic Dana locality is nonetheless world-class with respect to the size, variety, and quality of thomsonite. The Table Mountains additionally feature other rare zeolites in good quality, such as levyne and cowlesite. It has been nearly sixteen years since the last comprehensive article on this locality was published (Kile and Modreski 1988), and although many outstanding specimens have since been recovered, there have been no reported new species, and no substantial revision to the paragenetic sequence as presented earlier has been found necessary. Accordingly, much of the descriptive geology and mineralogy has been abstracted from the earlier report; the present

Crystal growth experiments were conducted using potassium alum and calcite crystals in aqueous solution under both non-stirred and stirred conditions to elucidate the mechanism for size-dependent (proportionate) and size-independent (constant) crystal growth. Growth by these two laws can be distinguished from each other because the relative size difference among crystals is maintained during proportionate growth, leading to a constant crystal size variance (beta(2)) for a crystal size distribution (CSD) as the mean size increases. The absolute size difference among crystals is maintained during constant growth, resulting in a decrease in size variance. Results of these experiments show that for centimeter-sized alum crystals, proportionate growth occurs in stirred systems, whereas constant growth occurs in non-stirred systems. Accordingly, the mechanism for proportionate growth is hypothesized to be related to the supply of reactants to the crystal surface by advection, whereas constant growth is related to supply by diffusion. Paradoxically, micrometer-sized calcite crystals showed proportionate growth both in stirred and in non-stirred systems. Such growth presumably results from the effects of convection and Brownian motion, which promote an advective environment and hence proportionate growth for minute crystals in non-stirred systems, thereby indicating the importance of solution velocity relative to crystal size. Calcite crystals grown in gels, where fluid motion was minimized, showed evidence for constant, diffusion-controlled growth. Additional investigations of CSDs of naturally occurring crystals indicate that proportionate growth is by far the most common growth law, thereby suggesting that advection, rather than diffusion, is the dominant process for supplying reactants to crystal surfaces.

Chemical analyses and crystal structure refinements were performed on lithian siderophyllite-3 T crystals from granitic pegmatites of the anorogenic Pikes Peak batholith (Colorado) to characterize the crystal chemistry and relations with trioctahedral lithium-bearing micas showing different stacking sequences. Chemical data show that the studied samples fall on the siderophyllite-polylithionite join, closer to the siderophyllite end-member. Single-crystal X-ray refinements were carried out on three samples (two of which were taken from core and rim of the same crystal) in space-group P 3 1 12 (the agreement factor, R obs , varies between 0.034 and 0.036). Mean bond distances and mean electron counts of M1, M2 and M3 octahedral sites indicate an ordered cation distribution with M1 and M3 positions substantially larger than M2. In the sample with the largest iron content, the M2 mean electron count increases as well as the mean distance, whereas remains smaller than or . The tetrahedral cation-oxygen atom mean distances range from 1.614 to 1.638 A and from 1.663 to 1.678 A for T1 and T2 sites, respectively, being consistent with Al 3+ enrichment in the T2 sites. The tetrahedral rotation angle, α, is generally small (3.1 ≤ α ≤ 4.6°) and decreases with siderophyllite content. As Fe increases, the T1 tetrahedron becomes flatter (112.4 ≤ τ T1 ≤ 110.5°), whereas T2 tetrahedron distortion appears unchanged (110.7 ≤ τ T2 ≤ 110.9).

Geological interpretations of crystal size distributions (CSDs) depend on understanding the crystal growth laws that generated the distributions. Most descriptions of crystal growth, including a population-balance modeling equation that is widely used in petrology, assume that crystal growth rates at any particular time are identical for all crystals, and, therefore, independent of crystal size. This type of growth under constant conditions can be modeled by adding a constant length to the diameter of each crystal for each time step. This growth equation is unlikely to be correct for most mineral systems because it neither generates nor maintains the shapes of lognormal CSDs, which are among the most common types of CSDs observed in rocks. In an alternative approach, size-dependent (proportionate) growth is modeled approximately by multiplying the size of each crystal by a factor, an operation that maintains CSD shape and variance, and which is in accord with calcite growth experiments. The latter growth law can be obtained during supply controlled growth using a modified version of the Law of Proportionate Effect (LPE), an equation that simulates the reaction path followed by a CSD shape as mean size increases.

Crystal-structure refinements were done on Li-bearing muscovite-2 M 1 crystals from microgranite and granitic pegmatite rocks in order to characterize their crystal chemistry and their relationships with muscovite and trioctahedral lithium-containing micas. In addition to the substitution mechanism [6] Li + [6] Al 3+ −1 [4] Al 3+ −2 [4] Si 4+ 2 , Li-bearing muscovite shows additional substitutions, such as mechanism [6] Li + [6] Fe 2+ [6] Al 3+ −1 [6] □ −1 , indicating that the structure deviates from ideal dioctahedral character. Single-crystal X-ray-diffraction data were collected for five crystals in space group C 2/ c ; the agreement factor, R obs , varies between 0.033 and 0.042. The mean tetrahedral cation–oxygen atom distances range from 1.637 to 1.646 A and from 1.629 to 1.647 A for T 1 and T 2 sites, respectively. Variation in T –O> distances is associated with the Li + /(Li + + Al 3+ ) ratio, octahedral M 2 site expansion (9.30 ≤ volume M2 ≤ 9.90 A 3 ) and reduction in size of the M 1 site. Moreover, as the Li + /(Li + + Al 3+ ) ratio increases, the silicate ring becomes less distorted (5.9 ≤ α ≤ 11.4°), the basal oxygen-atom planes become less corrugated (0.147 ≤ Δ z ≤ 0.232 A), and the interlayer separation narrows (3.337 ≤ interlayer separation ≤ 3.422 A).

The crystal structure and M-site populations of a series of micas-1M from miarolitic pegmatites that formed within host granitic rocks of the Precambrian, anorogenic Pikes Peak batholith, central Colorado, were determined by single-crystal X-ray diffraction data. Crystals fall in the polylithionite-siderophyllite-annite field, being 0 less than or equal to Li less than or equal to 2.82, 0.90 less than or equal to Fe-total less than or equal to 5.00, 0.26 less than or equal to([6])Al less than or equal to 2.23 apfu. Ordering of trivalent cations (mainly Al3+) is revealed in a cis-octahedral site (M2 or M3), which leads to a lowering of the layer symmetry from C12/m(1) (siderophyllite and annite crystals) to C12(1) diperiodic group (lithian siderophyllite and ferroan polylithionite crystals). On the basis of mean bond length the ordering scheme of octahedral cations is mostly meso-octahedral, whereas the mean electron count at each M site suggests both meso- and hetero-octahedral ordering, the calculated mean atomic numbers being M1 = M3 not equal M2, M2 = M3 not equal M1 and M1 not equal M2 not equal M3. As the siderophyllite content increases, so do the a, b, and c unit-cell parameters, as well as the refractive indices, primarily np. The tetrahedral rotation angle, alpha, is generally small (1.51 less than or equal to alpha less than or equal to 5.04 degrees) and roughly increases with polylithionite content, whereas the basal oxygen out-of-plane tilting, Delta z, is sensitive both to octahedral composition and degree of order (0.0 less than or equal to Delta z less than or equal to 0.009 Angstrom for siderophyllite and annite, 0.058 less than or equal to Delta z less than or equal to 0.144 Angstrom for lithian siderophyllite and ferroan polylithionite crystals).

The sorption isotherms of ethylene dibromide (EDB), diuron (DUN), and 3,5-dichlorophenol (DCP) from water on the humic acid and humin fractions of a peat soil and on the humic-acid of a muck soil have been measured. The data were compared with those of the solutes with the whole peat from which the humic-acid (HA) and humin (HM) fractions were derived and on which the sorption of the solutes exhibited varying extents of nonlinear capacities at low relative concentrations (C-e/S-w). The HA fraction as prepared by the density-fractionated method is relatively pure and presumably free of high-surface-area carbonaceous material (HSACM) that is considered to be responsible for the observed nonlinear sorption for nonpolar solutes (e.g., EDB) on the peat; conversely,the base-insoluble HM fraction as prepared is presumed to be enriched with HSACM, as manifested by the greatly higher BET-(N-2) surface area than that of the whole peat. The sorption of EDB on HA exhibits no visible nonlinear effect, whereas the sorption on HM shows an enhanced nonlinearity over that on the whole peat. The sorption of polar DUN and DCP on HA and HM display nonlinear effects comparable with those on the whole peat; the effects are much more significant than those with nonpolar EDB. These results conform to the hypothesis that adsorption onto a small amount of strongly adsorbing HSACM is largely responsible for the nonlinear sorption of nonpolar solutes on soils and that additional specific interactions with the active groups of soil organic matter are responsible for the generally higher nonlinear sorption of the polar solutes.

Calcite crystal growth experiments were undertaken to test a recently proposed model that relates crystal growth mechanisms to the shapes of crystal size distributions (CSDs). According to this approach, CSDs for minerals have three basic shapes: (1) asymptotic, which is related to a crystal growth mechanism having constant-rate nucleation accompanied by surface-controlled growth; (2) lognormal, which results from decaying-rate nucleation accompanied by surface-controlled growth; and (3) a theoretical, universal, steady-state curve attributed to Ostwald ripening. In addition, there is a fourth crystal growth mechanism that does not have a specific CSD shape, but which preserves the relative shapes of previously formed CSDs. This mechanism is attributed to supply-controlled growth.All three shapes were produced experimentally in the calcite growth experiments by modifying nucleation conditions and solution concentrations. The asymptotic CSD formed when additional reactants were added stepwise to the surface of solutions that were supersaturated with respect to calcite (initial Omega = 20, where Omega = 1 represents saturation), thereby leading to the continuous nucleation and growth of calcite crystals. Lognormal CSDs resulted when reactants were added continuously below the solution surface, via a submerged tube, to similarly supersaturated solutions (initial Omega = 22 to 41), thereby leading to a single nucleation event followed by surface-controlled growth. The Ostwald CSD resulted when concentrated reactants were rapidly mixed, leading initially to high levels of supersaturation (Omega >100), and to the formation and subsequent dissolution of very small nuclei, thereby yielding CSDs having small crystal size variances.The three CSD shapes likely were produced early in the crystallization process, in the nanometer crystal size range, and preserved during subsequent growth. Preservation of the relative shapes of the CSDs indicates that a supply-controlled growth mechanism was established and maintained during the constant-composition experiments. CSDs having shapes intermediate between lognormal and Ostwald also were generated by varying the initial levels of supersaturation (initial Omega = 28.2 to 69.2) in rapidly mixed solutions.Lognormal CSDs were observed for natural calcite crystals that are found in septarian concretions occurring in southeastern Colorado. Based on the model described above, these CSDs indicate initial growth by surface control, followed by supply-controlled growth. Thus, CSDs may be used to deduce crystal growth mechanisms from which geologic conditions early in the growth history of a mineral can be inferred. Conversely, CSD shape can be predicted during industrial crystallization by applying the appropriate conditions for a particular growth mechanism. Copyright (C) 2000 Elsevier Science Ltd.