Chalcedony
Автор:
Jesse Russell,Ronald Cohn, издатель:
"VSD", ISBN:
978-5-5108-8110-3
High Quality Content by WIKIPEDIA articles! Chalcedony ( /k?l?s?d?ni/) is a cryptocrystalline form of silica, composed of very fine intergrowths of the minerals quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigo