Horns are a form of keratin found on male antelopes, cattle, muskox, sheep, and goats, among other animals.  Unlike antlers, horns are permanent and are not made of bone.  Because of this, horn is much softer and less dense than antler and are generally not suitable for heavy percussion flaking.  However, horn pressure flakers are known from the archaeological record, and horn hammers are used as a type of indirect percussion hammer by modern flintknappers in India.