Specimens of geodes containing both quartz and calcite crystals from Morocco.Geodes form as bubbles of gas within magma (the term for lava when the molten rock is still underground). Because of the temperatures difference between the magma and the pocket of gas, the crystals form slower, crystals which form slower tend to form in larger sizes and so with a geode, you have an outside which is made up of very fined grained crystals, too small to see and the inside, which is full of larger crystals. These particular specimens are geodes which contain dogtooth calcite crystals and quartz crystals, it is believed that the mineral constituents changed over time from silicates to carbonates causing these geodes to have both calcite and quartz crystals. These samples are ideal for teaching about geode formation but would also make an excellent addition to any mineral collection. Specimens are supplied in a white card tray with an information label.