Types of Sun Reflecting Rocks for a Rock Garden

Granite

• Granite is a rock that forms from volcanic lava cooling underground. The rock has both quartz and mica minerals among others. The mineral grains in quartz are medium to coarse and easily visible with the naked eye. Quartz and mica have shiny or flat surfaces that reflect sunlight as it hits the rock. The minerals in quartz are usually white, pink, black and clear that appear mixed throughout the rock, which makes it attractive in a rock garden.

Slate

• Slate rock has two types of mica minerals that give the rock a shiny appearance. Slate can also have a variety of other minerals in its matrix. The mineral grains in slate are very fine and too small for the naked eye to see. However, the abundance of the micas reflects the sunlight as it hits the rock, making the surface very shiny. Slate slabs are common in a garden setting, giving a large surface area for the sun's rays to reflect.

Schist

• Schist is another quartz and mica-rich rock. This rock forms from metamorphic settings with high heat and pressure. The pressure causes the mica minerals to line up, which give the appearance of sheets of mica on the surface of the rock. The sunlight reflects off the layers of aligned mica grains.

Obsidian

• Obsidian is a black, volcanic glass rock that has no visible mineral grains. The rock is very shiny on all surfaces and reflects sunlight well in a rock garden. You should take care with the samples if you use the rock because a broken piece can have very sharp edges and may cut you as you build the rock garden. You may also notice a swirl pattern on the broken piece, which is a fracture pattern on the rock surface.