It was noted as being one of the natural wonders on the Romulan homeworld. The history of the forest was linked to the Allerash Mountains which, millions of years ago, had one of its volcanoes erupt with the act completely covering the region of the nearby small forest with magma and ash. The trees died but as time passed the minerals in the lava and ash filtered into the wood that petrified as well as preserved it. This led to a soft stone around the petrified trees that eroded away and left the tree's standing as stony monuments to their former life of verdancy. Tiny flakes of mica and similar minerals in the bark gave the trees a glittering and sparkling appearance in the light of the sun and the moon.
These qualities led to the forest transforming into the "jeweled" forest that was unlike anything in the rest of the galaxy and drew in thousands of Romulan sightseers. (Last Unicorn RPG module: The Way of D'era: The Romulan Star Empire)