Sandstones

Sandstone is an arenaceous sedimentary rock composed mostly of feldspar and quartz and varies in colour (in a similar way to sand), through grey, yellow, red, and white. Since sandstones often form extremely visible cliffs and other rock formations, certain colors of sandstone may be strongly identified with certain regions. For instance, much of the North American West is familiar for its red sandstones.

British Half Penny coin

100 The British decimal Half Penny or Ha'penny coin was issued on 15 February 1971, the day the British currency was decimalized. In put into practice it had been available from banks in bags for some weeks previously.

The main idea behind the coin's configuration was to enable certain pre-decimal coins—most notably the sixpence—to remain in circulation during the transition to decimal coinage; in the same vein a decimal quarter-penny coin was also proposed, but ended up never being formed.

The coin was minted in figurine. The coin weighed 1.78 grams and had a diameter of 17.14 millimeters. It was the smallest coin used in the decimal currency coinage by both size and value, and was nicknamed the "tidier" on account of its size. By the early 1980s its value was minimal and its main utility was as a useful driver of small screws. The 1984 half penny was only issued in mint and proof sets by the Royal Mint, and the coin was demonetized and withdrawn from circulation in December 1984.

The reverse of the coin, designed by Christopher Ironside, was simply a crown, with the fraction "½" below the crown, and either NEW PENNY or HALF PENNY above the crown.

Tumor

Tumor or tumour is an irregular growth or mass of tissue. A tumor can be either malignant or benign. Almost all tumors are examples of neoplasia, although certain developmental malformations or inflammatory masses may occasionally be referred to as tumors.

Neoplastic tumors are caused by mutations in DNA of cells, which interfere with a cell's capability to regulate and limit cell division. An accumulation of mutations is needed for a tumor to emerge. Mutations that activate oncogenes or repress tumor suppressor genes can eventually lead to tumors. Cells have mechanisms that repair DNA and other mechanisms that cause the cell to destroy itself by apoptosis if DNA damage gets too severe. Mutations that repress the genes for these mechanisms can also ultimately guide to cancer. A mutation in one oncogene or one tumor repressor gene is usually not enough for a tumor to occur. A combination of a number of mutations is essential.