rhyolite :
a volcanic rock of continental (felsic) composition. Typically rhyolites are light gray or pink, but they can be a variety of other colors. Granite is its coarse-grained equivalent.
a volcanic rock of a mixed composition, typically found at convergent plate boundaries (where continental and oceanic materials are coming together). The andesite in our tray include some hornblende crystal that formed at the magme came up the volcano.
a volcanic rock of oceanic (mafic) composition. Typically very dark, these rocks form the bottom of the sea floor, oceanic volcanoes such as Hawaii, and in situation where mantle magmas work their way through the continental crust without much mixing.
a coarse-grained typically light-colored igneous rock formed in continental area. Typical granites have common quartz and perhaps two or more varieties of feldspar, with some biotite, hornblende or muscovite.
typically have a gray or salt-and-pepper mix, containing some of the minerals typical or granites and gabbros.
a corase-grained dark-colored igenous rock found in oceanic areas. Typically composed of light to dark gray Calcium plagioclase and dark pyroxenes.
a volcanic glass. Glass forms from molten quatrz. Obsidian is a natural glass. It forms when a quartz magma is thrown out of a volcano and cools rapidly. Because it is a pure quartz it has a glassy fracture, which made it a valuable material for making arrowheads.
basically a petrified froth. The upper part of a lava flow can have air that is mixed into the liquid and is trapped there when the magma cools. This rock is sometimes ground up to use as an abrasive in soap (LavaÔ) or in "stone-washing" blue jeans.
basically a petrified volcanic froth of basaltic composition, sometimes call a "vesicular basalt." This is basically the basaltic equivalent of pumice.
Peridotite is sometimes refered to as "ultramafic" since it has even more of the mafic materials than does basalt and gabbro. This rock is essentially formed of ferromagnesian minerals crystals. The peridotites in our trays are composed primarily of olivene, and have a very olivene look to them.
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andesite : 
basalt : 
granite : 
diorite : 
gabbro : 
Obsidian :
Pumice : 
Scoria :
Peridotite :