Blue oval turquoise earrings

Blue Turquoise earrings made with oval shape turquoises 30mmx18mm.
The hook is in sterling silver.
Turkey, formerly country of commercial transit of turquoise, gave him its name.
Its synonym "Callaïte" (of the Greek "beautiful stone"), is employed little.
Turquoise was regarded as an amorphous stone until 1911, date where were discovered Turquoise crystals in Virgine (the USA). Hardness on the MOHS scale of hardness: 5-6. Density: 2,60-2,80