Sears offers this Lab-Created White Sapphire Heart Pendant in Sterling Silver, model no. 2SSRN96S/18, for $14.99. Apply coupon code "FEB15" to knock it to $12.74. With free shipping, that's $2 under yesterday's mention and a very low price for this kind of pendant. It features an 18" chain.
At Target, buy one select women's jewelry item and get 50% off a second. (Discount applies in-cart.) Shipping starts at $4.99, although orders of $50 or more qualify for free shipping. Either way, that drops a number of items to the lowest total price we could find. A couple of best bets, with prices before the above discount and $4.99 shipping: