Magnet Cove minerals are famous for being black, or having black on black minerals. Difficult to photograph? Yes they are! Here's some photos, as best as we can do.
|
The fellow who discovered the cavity accidently fell into the hole while walking down the creek bank. After his broken leg healed, he returned with a helper and excavated the pocket. It began at creek level and extended 18 feet below the normal stream water level. This piece is about 5 inches in height. |
|
Terminated aegirine crystal in pegmatitic host rock. Many examples of this mineral were sent to Europe before 1850 before it was properly identified. People thought it was black tourmaline! The aegirine crystal is 3 inches long by 1/2 inch wide. |
|
Clusters of magnetite crystals are sometimes recovered loose in the soils of the central core of the intrusion. Most attractive specimens come from the weathering of calcite-rich carbonatite. Individual magnetite crystals are 1 inch across. |
 Brookite on smoky quartz has been collected in the Magnet Cove area since before 1850. Attractive large crystals are scarce, whereas smaller crystals are abundant in the soils at several locations. Silica for the formation of smoky quartz came directly from the host rock, the Arkansas Novaculite. These brookite crystals measure 1/2 inch across and 3/8ths inch thick. |
 Weathered biotite (mica) showing growth zones in a relatively well formed crystal. The mineral is probably now converted to vermiculite. Flakes and small books are relatively abundant in the residual soils of the core area. Because mica splits easily into thin sheets, it is called a "book" when the crystals have some thickness. Some books of vermiculite over 6 inches across and 2 inches in thickness were recovered in the early 1960's. The specimen is 1 inch tall and 1/4 inch thick. |
 Rutile paramorph after brookite. A paramorph is a mineral of the same chemical composition, but which crystalizes in a different crystal system as the original it replaced. In this specimen, brookite formed first and as the temperature rose, rutile began to replace it. Both minerals have the same chemical formula, but are stable at different temperatures. So this example retains the external crystal shape (form) of brookite, but is now composed of numerous interlocking small crystals of rutile. This crystal fits into a 1 1/4 inch perky box. |
|
Small rutile eightling mounted in a 1 1/4 inch perky box. Rutile eightling twins are perhaps the most famous mineral form known from Magnet Cove. Many were discovered by early collectors, but presently only a few collectors have been able to gain access to where they occur loose in the soils. Note thumbnail for size comparison. |
Rice-ball rosettes of albite. Several hundred pounds of specimens from thumbnails to large cabinet size were recovered from a cavity on the south side of Cove Creek.
Ch 3, page 4a
Contact the authors of Rockhounding Arkansas Revised Oct 1999
© Rockhounding Arkansas 1998 http://rockhoundingAR.com