Vesuvianite, Ca10(Mg,Fe)2Al4(SiO4)5(Si2O7)2(OH)4 (Calcium Magnesium Iron Aluminum Silicate Hydroxide), is an interesting mineral found originally on Mt Vesuvius, hence the name. Otherwise it is also known as Idocrase from the Greek meaning mixed form, referring to its crystals showing a mixture of other mineral forms. The mineral forms as a result of contact metamorphism on impure limestones and is usually found with other exotic silicates. A massive green gem variety is called Californite after the location where it was first found.

Description: Several brown elongated crystals in a white matrix of limestone. The largest is approximately 1cm in length, all having pyramidal terminations upon a crystal body with a square cross section. Approximately 20 intermediate sized crystals are found around the matrix, together with dozens of small crystals up to 2mm across.

Location: Coahuilla, Mexico.