Telling the type is pretty difficult, but not impossible. I know there are some websites with pics of different varieties, but unfortunately I don't have links at hand. even with pics, it's not easy to tell what type. In addition, there are some varieties that are only ornamental and not good for brewing. Unless your friend dried the hops, sealed them tightly (vacuum sealing is best) and kept them in a freezer, they may not be in very good shape. If it was me, I'd tell him thanks for the offer but skip it. Or you can just be adventurous and brew with them and hope for the best.