Sulphur—a well-known element occurring native in volcanic regions; also formed by the decomposition of sulphides, particularly pyrites.
Talc—a hydrous magnesium silicate; usually in foliæ; granular or fibrous forms; also compact; easy cleavage into thin flexible laminaæ, but not elastic; feel greasy; luster pearly on cleavage surface; apple-green to silvery white; H. 1–2; a secondary product from the alteration of magnesian minerals; distinguished by its soft, soapy feel, soapstone being one variety; whitish form is known as French chalk.
Titanite—calcium-titano-silicate; monoclinic; luster adamantine to resinous; brown, gray, yellow, green, and black; H. 5–5.5; occurs in various crystalline rocks.
Topaz—an aluminum silicate, with part of the oxygen replaced by fluorine; orthorhombic; H. 8; luster vitreous; colorless, straw-yellow verging to various pale shades, grayish, greenish, bluish, and reddish; distinguished by its hardness and infusibility; occurs in crystalline rock.
Tremolite—a calcium-magnesium amphibole; a common constituent of certain crystalline rocks.
Viridite—a general term used for green products of rock alteration, usually hydrous silicates of iron and magnesia; mainly chlorite.
Wad—bog manganese; a variety of psilomelane (q.v.).
Zeolite—a group of minerals derived from the alteration of various aluminous silicates.
Zircon—zirconium silicate; H. 7.5; luster adamantine; pale yellowish, grayish, yellowish green, brownish yellow, and reddish brown; infusible; occurs characteristically in square prismatic forms; found in crystalline rocks and granular limestone.