Hand samples of several rocks are shown in these photographs. The granite is pink in colour, from the colour of the feldspars in the matrix. The rhyolite is too fine-grained to distinguish individual crystals. This rock is volcanic, and was emplaced in a high-temperature flow; some flow features (banding, near horizontal in the photo) can be seen. The andesite sample is also finegrained, but the photo shows little more than the colour. Diorite has the same bulk chemistry, and the photo shows clearly the coarse crystals of hornblende (black) against the background of feldspars. The peridotite has a greenish tinge, perhaps because of the olivine content, although the samples in lab class are black and mostly composed of pyroxenes, the other major component to be expected.