This book examines the various geological reports on Nigerian geology which indicate that gemstones occur in all the geologic units of Nigeria. They are however concentrated within the 400km long and 150km wide NE-SW trending pegmatite belt of central Nigeria.Sapphire and emerald are the recognized precious stones while tourmaline, amethyst, topaz, zircon,garnet, and aquamarine constitute the common semi-precious stones in Nigeria. Their reserves are however not well known due to non systematic exploration. Over 90% of the Nigerian gems are exported illegally and are won in an environmentally unfriendly manner.At present, only one lapidary situated in Jos exist in the country. Many Nigerians can afford the loupe, filter and dichroscope and become proficient in gem identification. With few months of training, Nigerians can become skilled lapidarists. Processing of gems is involves; sawing, performing, dopping,calibrating, faceting and polishing. Pear, round,octagon, square, oval, marquise, triangle and heart shapes of different sizes are cut and polished in Nigeria.The demand for cut and polished Nigerian gems which has several uses is on the increase internationally.