PRL style horizontal line in Latex

Here's an elementary, yet visually similar, approach:

\documentclass{article}
\usepackage{graphicx,lipsum}% http://ctan.org/pkg/{graphicx,lipsum}
\newcommand{\PRLsep}{\noindent\makebox[\linewidth]{\resizebox{0.3333\linewidth}{1pt}{$\bullet$}}\bigskip}
\begin{document}
\lipsum[1]

\PRLsep

\lipsum[2]
\end{document}

\PRLsep is a scaled/flattened version of $\bullet$ - 1/3 of \linewidth wide and 1pt tall.

I extended the example. Now, you can write a text between the seperator. But it is not perfect. The length measurement of \blacktriangleleft gives 7.7778pt, but this includes the white space arround it. So this space is also stretched. The calc-Package is required.

\newlength{\PRLlen}
\newcommand*\PRLsep[1]{\settowidth{\PRLlen}{#1}\advance\PRLlen by -\textwidth\divide\PRLlen by -2\noindent\makebox[\the\PRLlen]{\resizebox{\the\PRLlen}{1pt}{$\blacktriangleleft$}}\raisebox{-.5ex}{#1}\makebox[\the\PRLlen]{\resizebox{\the\PRLlen}{1pt}{$\blacktriangleright$}}\bigskip}
\PRLsep{Text}

With TikZ:

\documentclass[a4paper]{article}
\usepackage{tikz}
\usepackage{lipsum}

\newlength{\diamondrulelength}
\setlength{\diamondrulelength}{0.6\textwidth}
\newlength{\diamondrulethickness}
\setlength{\diamondrulethickness}{2pt}
\newcommand{\diamondrule}{\begin{center}\tikz{\fill[black] (0.5\diamondrulelength,0) -- (0,0.5\diamondrulethickness) -- (-0.5\diamondrulelength,0) -- (0,-0.5\diamondrulethickness) -- cycle;}\end{center}}

\begin{document}
\lipsum[1]

\diamondrule

\lipsum[1]
\end{document}