gypsum - sand selenite rose from a dry lake near Merzouga, Morocco
Selenite gypsum sand rose CaSO4・2H2O
Selenite gypsum sand roses form in seasonal desert lakes as they dry. These unusual selenite “desert roses” were newly discovered in 2018 in Dyet Sriji, a seasonal salt lake west of the village of Merzouga, Morocco, in the Sahara Desert near the Algerian border. Dyet Sriji is dry in summer.
Selenite is typically transparent, but when it crystallizes in sandy conditions it forms rosettes of flattened crystals, the rose “petals,” which are either encrusted with sand or with sand embedded throughout.
Unlike the white-edged desert roses you see for sale in rock shops, these are unaltered and completely natural. Since gypsum has two attached water molecules, mineral dealers cook selenite roses with a weed burner to drive off the water, turning the edges of the crystals white. They are not found like this naturally, and we prefer that students see this mineral in unaltered form.
Here’s a photo of selenite roses from Mexico being burned to make the edges of the flattened crystals white. This is also how plaster is made. Gypsum is heated to above 130˚ Celsius to drive off roughly 75% of the water. When powdered, it becomes plaster. When water is added, the plaster rehydrates to become gypsum. Between two thick paper sheets, it becomes wallboard.
Select a specimen: You can select a specimen by telling us what is in the photo with it, a blue or black and silver pen, a black mechanical pencil or one of those plus some number of coins, or you can let us make the selection.
Making multiple purchases? Click on the "combine shipping" button in the shopping cart. We'll send an invoice with combined shipping. A link in that invoice will bring you back to checkout, no hassle.
Ships in a Regional Priority Mail box. There would be room in that box for other specimens at no increase in postage. Please request an invoice to avoid overpaying shipping, by clicking the "combine shipping" button in the cart. Click > Shipping < for shipping rates. Use back button to return to this page.