TETRADYMITE  , a See also:

• MINERAL

mineral consisting of See also:

• BISMUTH

bismuth telluride and sulphide, Bi2Te2S, also known as " telluric bismuth." Sometimes See also:

• SULPHUR

sulphur is absent and the See also:

• FORMULA
• FORMULA (Lat. diminutive of forma, shape, pattern, &c., especially used of rules of judicial procedure)

formula is then Bi2Tea; traces of See also:

• SELENIUM [symbol Se, atomic weight 79.2 (O=16)]

selenium are usually See also:

• PRESENT

present . Crystals are See also:

• RHOMBOHEDRAL

rhombohedral, but are rarely distinctly See also:

• DEVELOPED

developed; they are twinned together in See also:

• GROUPS
• GROUPS, THEORY

groups of four; hence the name of the mineral, from the See also:

• GREEK
• GREEK, ETRUSCAN AND

Greek, rerpaSupos, fourfold . There is a perfect cleavage parallel to the basal See also:

• PLANE

plane; and the mineral usually occurs in foliated masses of irregular outline . The See also:

• COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour is See also:

• STEEL, FLORA ANNIE (1847– )

steel-See also:

• GREY, CHARLES GREY, 2ND EARL (1764-1845)
• GREY, HENRY GREY, 3RD EARL (1802-1894)
• GREY, LADY JANE (1537-1554)
• GREY, SIR EDWARD
• GREY, SIR GEORGE (1812–1898)

grey, and the lustre metallic and brilliant . The mineral is very soft (H = 1) and marks See also:

• PAPER
• PAPER (Fr. papier, from Lat. papyrus)

paper; the specific gravity is 7.2 to 7.6 . It was first found, in 1815, at Telemarken in See also:

• NORWAY
• NORWAY (Norge)

Norway; crystals are from Schubkau near Schemnitz in See also:

• HUNGARY
• HUNGARY (Hungarian Magyarorszdg)

Hungary . It often occurs in See also:

• QUARTZ

quartz associated with native See also:

• GOLD
• GOLD [symbol Au, atomic weight 195.7(H = 1),197.2(0 =16)]

gold . Other See also:

• SPECIES

species very similar to tetradymite, but with different formulae, are: joseite, from See also:

• SAN

San Jose near Marianna in See also:

• BRAZIL
• BRAZIL, or BRASIL

Brazil; grunlingite (Bi,SaTe), from Caldbeck Fells in Cumber-See also:

• LAND

land; and wehrlite, from Hungary . (L . J .