Buying gems or jewelry can be challenging even when one has access to a fully equipped lab. However, most purchases are actually made in environments that make it difficult to carry anything more than a loupe, a flashlight, and a pair of tweezers. Practice with these and the additional portable gem instruments described in this article will enable the buyer to develop the keen senses needed to better ascertain the identity and quality of the material being considered. Practical tips that may be applied in the field are also included in each section. Common sense must dictate how a clue is applied, and some tests will merely help narrow down the possibilities.