Random Ramblings of a Rockhound Quiz

Answer: Granite

Rhyolite is an extrusive igneous rock formed by the rapid cooling of lava on the earth's surface. When the same lava (known as magma when found within the earth) cools and forms rocks within the earth's crust, it forms granite. Both rocks have a higher amount of silica and lesser amount of iron and magnesium.

Answer: Conglomerate

Sedimentary rocks with a grain size of 2 mm or more are known as rudaceous rocks. Most common examples of these types of rocks are conglomerates and breccias. The size of grains in sandstone range between 1/16th mm to 2 mm leading to the rock being categorized as arenaceous. Argillaceous rocks like shale are composed of very fine grains, mainly those of clay.

Marble is a metamorphic rock.

Answer: Rutile

Rutile, named after its deep red colour, is the most common form of titanium dioxide. Rarer forms of this oxide include minerals like anatase and brookite. Rutile occurs as an accessory mineral in igneous rocks such as pegmatite and granite as also metamorphic rocks like gneiss and schist. Though the mineral is attractive, its use in jewellery is restricted by its hardness of 6, which makes it vulnerable to scratches.

However, when tiny rutile inclusions in the form of needles are found in other gemstones like rubies and sapphires, they give rise to a phenomenon called asterism where light is reflected to form a star shape. Gemstones exhibiting this trait are much sought after.

Answer: Kidney shaped

The external shape of the crystals of a mineral is called the crystal habit. Haematite is one of the main ores of iron and is named after the Greek word for blood as the crystals are commonly found to be red in colour.

Answer: Ruby

Corundum is a mineral composed largely of aluminium oxide. It is one of the hardest known minerals with a hardness of 9 on the Mohs scale of hardness. When the crystals of the mineral are red in colour, the mineral is known as ruby. All other varieties are called sapphires.

Answer: Rock flour

Rock flour is also known as glacial flour and formed by the glacial erosion of the underlying bedrock. When the glacier melts, the fine particles are carried along with other sediments and finally deposited when the river meets a lake. The rock flour refracts light intensifying the blue colour of the lake. Moraine Lake and Peyto Lake in Banff, Canada owe their beautiful colours to this phenomenon.

Answer: Lake Baikal

Lake Baikal, located in the southern part of Siberia in Russia, is the deepest lake in the world. Designated as a UNESCO world heritage site in 1996, the lake is situated within an active rift valley. Other well known lakes like Lake Tanganyika in Africa and Lake Superior in North America are also found in rift valleys.

Answer: Eskers

Merriam-Webster defines an esker as "a long narrow ridge or mound of sand, gravel, and boulders deposited by a stream flowing on, within, or beneath a stagnant glacier". Another type of ridge formed by glacial activity is known as the arête. An arête is created when two glaciers moving in a parallel direction erode U-shaped valleys leaving only a thin ridge of rock between them.

Corporal Slag has planned a visit to the Eskers Provincial Park in British Columbia, Canada to study these features in more detail.

Answer: Sedimentary

Ripple marks are a form of sedimentary structure and are formed at the time the sediments are deposited. These structures later help to determine the original position of the strata when the marks were formed and also provide indicators of the type of environment that existed during the sediment deposition. Ripple marks are most often attributed to the action of water though they may also be formed by wind. Different types of ripple marks also help to understand if the water was flowing in one direction or the structure was formed by the ebb and flow of waves.

Answer: Quartz

Quartz occurs in all the three types of rocks - igneous, sedimentary and metamorphic. With a hardness of 7 on the Mohs scale, the mineral is quite resistant to weathering and hence commonly found in sedimentary deposits. Traces of different elements produce different varieties of quartz which are categorized based on their colour. Another variety of quartz which would've fit the theme of this quiz is rose quartz - a pink variety whose colour is generally attributed to small amounts of titanium or manganese found in the mineral.

Corporal Slag favours the purple variety better known as the gem stone, amethyst.