dolomite - teaching hand/display specimen of white Upper Ordovician dolomite
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This particular metamorphic rock can look like marble or it can look like limestone. In this case it looks like a fine-grained white marble. It differs from marble in having some or all of the calcium in calcium carbonate replaced by magnesium. This replacement can occur with or without metamorphic heating. Before metamorphism it was a limestone. If not heated and recrystallized, it would have looked just like the original limestone though some of the calcium had been replaced by magnesium.
If heated by deep burial or by a nearby intrusive body, limestone will recrystallize as in this specimen, taking on the appearance of marble.
Marble and limestone are calcium carbonate and effervesce freely with dilute hydrochloric acid. Dolomite, calcium-magnesium carbonate, will effervesce weakly and may need to be powdered as when lightly tapped by a geologist's hammer to encourage effervescence.
Students should compare this with marble, with limestone and with dolomite that looks like limestone. It will surprise them that dolomite can look both like crystalline marble and like sedimentary limestone.
These specimens were collected from the Lower Ordovician Ely Springs Formation in the Inyo Range in California.
If you are a science or earth science teacher purchasing this as a teaching specimen for your class, your students should compare this with marble, with limestone and with dolomite that looks like limestone. It will surprise them that dolomite can look both like crystalline marble and like sedimentary limestone.
Some of these specimens have been saw-cut flat on the back, and occasionally on an edge so they will fit in a unit tray. If you prefer an uncut specimen, ask and we'll let you know if one is available.
These specimens ship by Regional Priority Mail and can be combined with other purchases. They are too thick to fit in a small flat rate box.
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.