Customize the Genesis Search Box with Icon Fonts: http://rickrduncan.com/wordpress/genesis-search-box-dashicons

functions.php

<?php
//* Do NOT include the opening php tag


//* Enqueue FontAwesome. Note that the current version in the code is 4.5.0. Update as necessary.
//* https://codex.wordpress.org/Plugin_API/Action_Reference/wp_enqueue_scripts
//* https://fortawesome.github.io/Font-Awesome/icons/
<?php
//* Do NOT include the opening php tag

add_action( 'wp_enqueue_scripts', 'b3m_enqueue_styles' );
function b3m_enqueue_styles() {
	
	wp_enqueue_style( 'fa', '//maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css', array(), '4.5' );
	
}

//* Customize Genesis search form input button text
add_filter( 'genesis_search_button_text', 'b3m_search_button_text' );
function b3m_search_button_text( $text ) {
	
	return esc_attr( '&#xf002;' );

}

styles.css

.search-form {
	position: relative;
}

.search-form > input {
    padding-left: 40px;
}

.search-form input[type="submit"] {
    background: none !important;
    border: none;
    clip: inherit;
    color: #4a545a;
    display: inline-block;
    font-family: 'FontAwesome';
    font-size: 28px;
    height: 38px;
    padding: 0 10px 0 12px;
    position: absolute;
    left: 2px;
    top: 12px;
    vertical-align: top;
    width: 38px;
}