The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
Large facetable gems from Hotazel, South Africa are available, but larger clean stones are very scarce and expensive. Pink rhodochrosite from Colorado in clean gems is prized but also expensive. Any Colorado gem over 2-4 carats is considered very large. Argentinian material is translucent at best and much less costly, but few faceted gems from this material have appeared on the market. Mexican gem material resembles Colorado material but is generally quite small. Peruvian stones also resemble those from Colorado.