Link to lightbox gallery from category archive

Okay, I figured it out…

In the loop:

$attachments = get_children(array('post_parent' => $post->ID,
                        		'post_status' => 'inherit',
                        		'post_type' => 'attachment',
                        		'post_mime_type' => 'image',
                        		'order' => 'ASC',
                        		'orderby' => 'menu_order ID'));

				foreach($attachments as $att_id => $attachment) {
    					$full_img_url = wp_get_attachment_url($attachment->ID);  ?>
					<a href='<?php echo $full_img_url; ?>' rel='lightbox[<?php the_ID(); ?>]' class='hidden' title='<?php echo get_the_title(); echo "<br />".$attachment->post_excerpt; ?>'></a>
				<?php }

And where the featured images display:

$image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'single-post-thumbnail' );?>
<a class="post-thumbnail" href="<?php echo $image[0]; ?>" rel="lightbox[<?php the_ID(); ?>]" title="<?php echo get_the_title();  echo '<br />'.$caption;?>" aria-hidden="true">
		      <?php
			the_post_thumbnail( 'post-thumbnail', array( 'alt' => get_the_title() ) );
		      ?>
	              </a>