Crossite is an inosilicate double chain sodic amphibole and is a rare silicate mineral belonging to the riebeckite group. It is considered an intermediate between the amphiboles glaucophane and magnesioriebeckite, which form a series. IMA status: discredited 1997. Crossite is an inosilicate double chain sodic amphibole and is a rare silicate mineral belonging to the riebeckite group. It is considered an intermediate between the amphiboles glaucophane and magnesioriebeckite, which form a series. IMA status: discredited 1997. Crossite is named after Charles Whitman Cross, an American USGS petrologist.