\begin{table}%t1
%\begin{minipage}[t]{\columnwidth}
\caption{Astronomical and GEMS Composition Data.
\label{table1}}
%\centerline
 {\begin{tabular}{c c c c c c c}
\hline\hline
 & O/Si$^a$ & Mg/Si$\sp{a}$ & S/Si$\sp{a}$ & Fe/Si$\sp{a}$ & Isotopic composition & Reference \\
 \hline
 { Solar} & & 1.01 & 0.52 & 0.9 & & ~\citet{Anders1982} \\
 { Diffuse ISM} & & 1 & $<$0.12 & 0.9 & & ~\cite{Sofia2004} \\
 { Average (200 GEMS)} & NR$^b$ & 0.6 & 0.31 & 0.54 & & ~\citet{Keller2004} \\
 { Average (42 GEMS)} & NS ($+33\%$)$^{c,~ d}$ & 0.65 & 0.26 & 0.44 & & ~\citet{Ishii2008} \\
 \\
 {Anomalous GEMS} & & & & & & \\
GEMS 1 & S ($-1.3\%$)$^e$ & 0.75 & 0.31 & 1.3 & $\delta\sp{18}$O ($\permil$) $+238\pm12$ & isotopes: ~\citet{Floss2006} \\
& S ($-9.7\%$)$\sp{e}$ & 1.1 & 0.26 & 0.44 &  $\delta\sp{18}$O ($\permil$) $+238\pm12$ & and Mg/Si: this work\\
GEMS 2 & S & 0.72 & 0.19 & 0.48 & $\delta\sp{17}$O ($\permil$) $+523\pm85$ & bulk GEMS isotopic compositions:  \\
& \arcsec & \arcsec & \arcsec & \arcsec &  $\delta\sp{18}$O ($\permil$) $-100\pm37$ & ~\citet{Keller2007a} \\ 
GEMS 3 & \arcsec & 1.2 & 0.19 & 0.43 & $\delta\sp{18}$O ($\permil$) $+80\pm20$ & \arcsec \\
 & \arcsec & \arcsec & \arcsec & \arcsec & $\delta\sp{18}$O ($\permil$) $+145\pm30$ & subregion of GEMS 3 above \\
 GEMS 4 & \arcsec & 0.37 & 0.26 & 0.47 & $\delta\sp{18}$O ($\permil$) $-15\pm55$ & ~\citet{Keller2008} \\
 & \arcsec & \arcsec & \arcsec & \arcsec & $\delta\sp{17}$O ($\permil$) $+1220\pm260$ & \arcsec \\ 
 \hline
 \end{tabular}}
\par
 $^a$  {Typically $<$$5\%$ analytical uncertainty.}
 $^b$  {NR $=$ not reported.}
 $^c$   {NS $=$ non-stoichiometric (average 33\% excess O over stoichiometry).}
 $^d$  {Stoichiometry calculated by assigning O as MgO, SiO$\sb2$, Al$\sb2$O$\sb3$, CaO and S, Fe and Ni as sulfides and metal.}
 $^e$  {S $=$ stoichiometric (within analytical uncertainty of $\pm $$10 \%$).}
 \end{table}