The term 'blue gemstone' can refer to three different stones: SAPPHIRE, LAPIS, and lapislazuli. SAPPHIRE is an 8-letter word and is a precious gemstone that is typically blue in color. LAPIS is a 5-letter word and is a deep blue metamorphic rock that is composed of several minerals, including lazurite. Lapislazuli is an 11-letter word and is a combination of the two previous stones, with lazurite being the main component. All three of these stones are highly valued for their beauty and rarity.