Garnet is a very plentiful group of minerals found in nearly every igneous or metamorphic rock as an accessory because so many di- and trivalent elements can fit into the garnet structure. The most common garnet is probably almandine which is found in abundance as porphyroblasts in schist, in pegmatites, and very occasionally in gabbros and mafic metavolcanic rocks. Almandine in schist is typically associated with muscovite, biotite, quartz, staurolite, kyanite, sillimanite, plagioclase feldspar, chlorite, and others. Almandine can also be found in pegmatites as a very common accessory. Pegmatitic almandine typically has some manganese impurity and is in solid solution with spessartine. Well 
known localities for almandine are Roxbury, Connecticut, USA; Mahattan Island and Gore Mountain in New York; Peru, Maine; Calumet, Colorado; the Otz Valley and Zillertal in North Tyrol, Austria; numerous locations throughout Brazil; Gilgit, Pakistan; the Xinjiang Uyghur Autonomous Region, China; and Madagascar. The largest crystals in the world, which are up to around a meter in width are from Gore Mountain in New York where they are mined for industrial abrasive and gem rough.
Grossular garnets are another plentiful and colorful variety of garnet. Grossular forms in iron poor, calcium rich metamorphic rocks such as serpentinites and skarns. Orange grossular is sometimes known as hessonite and is found in gemmy crystals abundantly worldwide in both serpentinites and contact metamorphosed limestones. Famous localities for orange grossular garnets or hessonite are the Jeffrey Mine in Quebec, Canada; Minot, Maine; Val d’Ala, Torino, Italy; and the VAG Mine in Eden Mills, Vermont. Grossular of other colors are also found with realtive abundance worldwide. Yellowish or greenish grossular has been found near Kayes, Mali; the Vilyui River Basin in Sakha, Russia; and the Thetford Mines region, Quebec. Some of the grossular in the latter locality can be vivid green from chromium impurities. Some amazing pink Grossular has been found near Sierra de la Cruz, Coahuila, Mexico. Tsavorite, the extremely valuable and rare emerald green gemmy garnet is found at the Tsavo Preserve in Kenya. Unfortunately, most tsavorite crystals are cut into gemstones so specimens of this material are hard to find.
Andradite is another common species of garnet and is found in contact metamorphosed rock rich in iron such as skarns and in some serpentinites. Andradite is a common mineral found in metallic ore deposits, especially skarn associated copper, molybdenum, and tungsten ore veins. Well known localities for andradite garnets are Bishop, Inyo County, California for nice orange crystals; the New Idria District in San Benito County, California for yellow topazolite, greenish demantoid, and black melanite; Marmoraton Iron Mine, Ontario for blackish red crystals in skarn; Afghanistan for pale green demantoid; Val Malenco, Italy for yellow to green topazolite and demantoids on serpentinite; Tubussis Farm in Namibia for finely colored demantoid; Kohse Mine, Tenkawa, Nara, Japan for iridescent orange crystals; Kayes, Mali for giant black, deep red, and yellowish crystals; and Kerman, Iran for apple green chromian demantoid.
Spessartine garnet is a gorgeous orange form of garnet rich in manganese. It is primarily 
found in pegmatites but has also been reported from miarolytic granites and manganese deposits. Excellent spessartine is found as small crystals with smoky quartz, fluorite, microcline, and helvite in miarolytic granite in Tongbei, Zhangzhou Prefecture, Fujian Province, China; in manganese rich schists at Loliondo, Tanzania; as large orange crystals on pegmatite from Laghman, Afghanistan; Marienfluss, Namibia; Baltistan, Pakistan; Madagascar, Norway, Connecticut, and San Diego County, California. Spessartine is named after its type locality in Spessart, Germany.
Many other species of garnet are popular among mineral collectors. Uvarovite is the most popular out of these rarer species. It is associated with ultramafic rocks particularly those rich in chromium, copper, and nickel. It has been found at its best as druses of small bright green crystals from the Saranovskii Mine, Permskaya Oblast, Russia; and as large single deep green crystals in the Outokumpu ore field, Finland. Fine crystals of uvarovite have been reported as coming from Southern India but very little information has been available on this limited find.