The traditional heart shaped gemstone cut contains 59 facets and is, essentially, a pear cut gemstone with a cleft at the wider end. Heart shaped gemstones, however, are not limited strictly to a 59 facet cut. Two examples of heart cut gemstones that utilize a facet count other than 59 can be found on the Gram Faceting website (Faceters.com). In particular, the owner of Gram Faceting, Jeff Graham, shares two of his heart cut designs - the Simple Heart and the Heart Squared - that employ 44 facets and 67 facets, respectively.
The length-to-width proportions of the traditional heart cut
gemstone
are nearly identical. If you've shopped around for heart
shaped gemstone jewelry, you'll often notice that measurements such as,
"...a 10 mm heart.." are listed. This simply means that the
heart shaped gemstone in question has equal or near-equal
length-to-width dimensions.
Example (Not to Scale):