Replacing search button text with a icon font in Genesis. http://sridharkatakam.com/replace-search-button-text-icon-font-genesis/

functions.php

//* Make Font Awesome available
add_action( 'wp_enqueue_scripts', 'enqueue_font_awesome' );
function enqueue_font_awesome() {

	wp_enqueue_style( 'font-awesome', '//netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.css' );

}

//* Customize search form input button text
add_filter( 'genesis_search_button_text', 'sk_search_button_text' );
function sk_search_button_text( $text ) {
	return esc_attr( '' );
}

gistfile1.css

.search-form input[type="submit"] {
	font-family: FontAwesome;
}

gistfile2.css

.search-form input[type="submit"] {
	font-family: FontAwesome;
	background: none;
	border: none;
	color: #888;
	padding-left: 0;
	font-size: 2.2rem;
	vertical-align: middle;
}

.search-form input[type="submit"]:hover {
	background: none;
	border: none;
	color: #333;
}