Crystal Grottoes

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Crystal Grottoes is the only show cave in the U.S. state of Maryland. It is located on Maryland Route 34 between Boonsboro and Antietam National Battlefield.

[edit] History

These caves were discovered in 1920 in the course of quarrying operations by a road construction crew, trying to obtain gravel. A drill bit (for placing explosives) disappeared into a hole, and the crew realized they had found a cave. Blasting produced the entrance which is still used, and in 1922 the cave was opened to the public. A mapping operation in 1968 revealed about a half mile of passages, but only about one third of the cave is accessed during the tour, which takes about forty minutes.

A fire in December 2007 caused substantial damage to the visitors center.

[edit] Geology

Crystal Grottoes is an example of a karst cave, formed in a anticline in a bed of Tomstown Dolomite. When discovered most rooms of the cave were filled with clay, up to six feet in parts of the commercial tour route. There are no streams within the cave, though there is a pool fed by dripping water.

The rooms along the tour are very tall and narrow, up to sixty feet high. Most abound in formations, generally stalactites, flowstone, and columns. They are typically white or buff, with one area (called Fairyland) tinted a light blue, perhaps by copper oxides. In some parts of the cave, particularly toward the exit and in passages between larger rooms, the carbonates have dissolved to leave a clay matrix retaining the form of the original rock.

The largest room is the Blanket Room, measuring roughly thirty by twenty feet. Another notable area is the Golden Lake, the pool mentioned above. Parts of this pool are bridged by travertine formations, a feature also found in some of the nonpublic areas of the cave. Unlike at some other caverns the lighting is uncolored, allowing the visitor to see the formations' natural colors.