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sand - olivine - set of five tubes of olivine sand weathered from basalt with coral sand derived from a reef

$ 11.90

Sand is derived from whatever material is locally available. 

Beaches are uncommon on the seacliff-ringed Island of Hawaii.  Occasional small coves have sand derived primarily from basalt unless there is a coral reef offshore. This sand was collected in the 1994 from a tiny cove near South Point, Hawaii, where a local concentration of olivine had weathered out of the basalt and was concentrated by the waves. An offshore coral reef contributed about half of the grains in this sand.

Olivine forms at temperatures and pressures found in the earth's mantle and is carried up from a mantle hot spot in the basalt that forms the Hawaiian Islands. It is almost twice as dense as quartz, which is the typical source material of the white sand beaches of the continental USA, so it is not as easily swept out to sea by wave action. Because of the offshore reef, some grains of this sand are composed of coral or shell material. 

Hawaii's white sand beaches at Waikiki were initially an import, from California. In the 1920s and 1930s sand was barged from Long Beach, though the import of California sand was abandoned in the 1970s and the beach is now maintained with locally dredged sand composed of coral and shell fragments. A locally famous black sand beach occupies a cove southwest of Hilo, where the sand is entirely basalt. At Mahana Bay, where there is an often tourist-visited green sand beach, the greenish sand is composed of grains of olivine that weather out of the basalt of an old cinder cone. 

We had this sand in storage and thought it was entirely olivine. Interesting, since it shows that sand is composed of whatever material is available. The white grains are coral and some shelly material, black are basalt. Green grains are olivine.

Set of five tubes, 16 ml each, optically clear polystyrene with screw caps. The plastic tubes are practical in a classroom and are somewhat student resistant, though a cap can be unscrewed. Good for student examination. When this sand is gone, it's gone. A recent law prohibits removal of sand from Hawaii's beaches.




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