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E. S. McGee

Publications and source records attributed to E. S. McGee.

At least 19 recordsLinked to original sources
USGS1996

Development of gypsum alteration on marble and limestone

Blackened alteration crusts of gypsum plus particulates that form on sheltered areas on marble and limestone buildings pose a challenge for rehabilitation and cleaning. Fresh marble and limestone samples exposed at monitored exposure sites present conditions of simple geometry and well-documented exposures but have short exposure histories (one to five years). The gypsum alteration crusts that develop on these samples provide insight into the early stages and rate of alteration crust formation. Alteration crusts from buildings give a longer, but less well known exposure history and present much more complex surfaces for gypsum accumulation. Integrated observations and measurements of alteration crusts from exposure samples and from buildings identify four factors that are important in the formation and development of alteration crusts on marble and limestone: (1) pollution levels, (2) exposure to rain or washing, (3) geometry of exposure of the stone surface, and (4) permeability of the stone. The combination of these factors contributes to both the distribution and the physical characteristics of the gypsum crusts which may affect cleaning decisions.

ASTM Special Technical Publication↗
USGS1992

Gypsum accumulation on carbonate stone

The accumulation of gypsum on carbonate stone has been investigated through exposure of fresh samples of limestone and marble at monitored sites, through examination of alteration crusts from old buildings and through laboratory experiments. Several factors contribute to gypsum accumulation on carbonate stone. Marble or limestone that is sheltered from direct washing by rain in an urban environment with elevated pollution levels is likely to accumulate a gypsum crust. Crust development may be enhanced if the stone is porous or has an irregular surface area. Gypsum crusts are a surficial alteration feature; gypsum crystals form at the pore opening-air interface, where evaporation is greatest.

Conference Paper↗
USGS1987

Mineralogical characterization of the Shelburne Marble; a Vermont marble test stone used to study the effects of acid rain

The Shelburne Marble of Vermont has been used extensively in buildings and monuments and for this reason has been selected as a test stone for the National Acid Precipitation Assessment Program (NAPAP) stone exposure studies. Miner alogical characterization of fresh Shelburne Marble provides a basis for recognizing mineralogical changes that may occur in samples when they are weathered. The Royal variety of Shelburne Marble is a white marble with gray streaks of inclusions. It is predominantly composed of calcite (97%) but contains inclusions of dolomite, layer silicates, framework silicates, and non-silicates. The inclusions are heterogeneously distributed in the rock and commonly form linear clusters that are dominated by dolomite + phlogopite + rutile ± chlorite. Less abundant inclusions are: muscovite, talc, quartz, feldspar, pyrite and apatite. All of the minerals that comprise the Shelburne Marble have nearly end-member compositions. Mineral composition, grain size and associations of the inclusions may significantly contribute to the durability (or weakness) of marble used in buildings or monuments that are exposed to conditions of acid precipitation.

Open-File Report↗
USGS1986

Garnet megacrysts of the Williams diatremes, north-central Montana.

The physical characteristics of garnet megacrysts from the Williams diatremes are described, analysed and compared with other garnet megacryst suites. The only correlation found between the physical characteristics and the composition of the megacrysts related deep-red colour to high Cr content.-J.A.Z.

American Mineralogist↗