Hydrated blue crystalline form of copper sulfate(noun)
WordNet. Princeton University. 2010.
Use "blue stone" in a sentence
"There were striated ivory bracelets made from some creatures tusks and large hair ornaments of jade, hematite and a blue stone that I didn't know."
"They made their living through pastoralism, brigandage, and export of the few resources they had to offer, including pistachios and lapis lazuli—the Hindu Kush being the only known source for this precious blue stone in the ancient world."