4 AGATE. 



tion of Felspar on a large scale. H. 2 to 3, 

 S.G. 2-8 to 2*9. Occurs massive of various 

 shades of greenish-grey, passing into yellow- 

 ish-grey and yellowish-brown. Translucent. 

 Feels rather greasy. Yields to the nail. 

 Sectile. Fracture splintery. 



Comp. 4 Ai ^i + K iSi^ + 3 H. 



Analysis by Klaproth, i'rora China : 



Silica 54-50 



Alumina .... 34-00 

 Potash . . . .6-25 



Water .... 400 



Oxide of iron . . . 0-75 



99-60 



Localities. — English. Eestormel Koyal iron 

 mines, Cornwall ; of a pale flesh-colour. — 

 Welsh. Glyder Bach, Caernarvonshire. — 

 Irish. Luggannre lead-mines, co. VVicklow, 

 (pale green). — Foreign. Norway. Nagyag 

 in Transylvania. 



Name. From «.y(x.\(/.cf.^an image, and x/&;, 

 stone. 



Agalmatolite is brought from China, 

 carved into grotesque figures and chimney- 

 ornaments. It is distinguished by its che- 

 mical composition from Steatite, which al- 

 wavs contains magnesia, but no potash: 



Brit. Mus., Case 26. 



M. P. G. Horse-shoe Case, Nos, 1102, 

 1109, 1112. 



Agaphite. See Turquois. 



Agate. A variegated variety of chalce- 

 donic Quartz, the colours of which are 

 arranged in clouds, spots, or bands. Tiie 

 latter consist of parallel or concentric layers, 

 either straight (ribbon agate), circular, or 

 in zigzag forms, the latter receiving the 

 name of fortification agate from the fancied 

 resemblance of the bands to the angular 

 outline of a fortification. 



Agates are found in Scotland, Saxony, 

 Arabia, India, Surinam, &c. in amygdaloid, 

 mostly in the form of hollow balls or geodes, 

 coated inside with Quartz or Amethyst. 



Immense quantities of Agate are cut and 

 polished at Oberstein in Khenish Bavaria, 

 and at Galgernberg in the north of Germany, 

 whence they are exported to all parts of the 

 -world.* There is also a manufactory at 

 Katherinenberg in Siberia. 



* " The agate trade at OI)erstein and Tdal has 

 lately undergone a singular change in consequence 

 of a tailing oft' in the supply of the agate nodules. 

 The agates now worked in that district, and sold 

 as native productions, are chiefly obtained from 

 the Brazils, where, on the Paraguay, brought 

 down from the interior by the Rio de la Plata, 

 they are in such abundance as to be shipped for 

 ballast. Notwithstanding the source of supply is 



AGARIC MINERAL. 



Agates are used for burnishers, and are 

 made into mortars for chemical purposes. 

 They are al§o much employed in a polished 

 state for ornamental articles, as brooches, 

 bracelets, beads, the handles of seals, paper- 

 knives, daggers, &c. The brooch-stones 

 sold by the name of Scotch pebbles are true 

 Agates, found in the amygdaloid of Dunbai', 

 and of the Hill of Kinnoul, near Perth ; but 

 the stones found in the Isle of Wight and 

 sold in a polished state under the name of 

 Agates, are merely flints from the Upper 

 Chalk, much of the beauty of which is de- 

 rived from the silicified remains of sponges ■ 

 and other marine bodies. 



The colours of Agate, when indistinct, 

 may be increased by boiling first in oil, 

 and afterwards in sulphuric acid; the latter 

 process carbonising the oil which has been 

 absorbed between the layers, heightens the 

 contrast between their different tints. 



The imperial treasury of France possesses 

 some beautiful works in Agate, consisting of 

 a service valued at 500,000 francs (20,000/.) 

 Several very beautiful articles were ex- 

 hibited at the Exhibition of 1851, from 

 Oberstein, and obtained prize medals. 



The name is derived from that of the river 

 Achates, whence, according to Theophrastus, 

 agates were first brought. 



Brit. Mus., Case 23. 



31. P. G. A 11 in Hall ; inlaid slab of 

 Agates, Jaspers, &c., from Aberystw^ith in 

 North Wales. Principal floor. Case 51, — a 

 suite of 87 specimens, illustrative of the for- 

 mation and mode of occurrence of Agates. 

 Horse-shoe Case, Nos. 571, 572, 583, 585, 

 657. 



Agaric Mineral, Kirwan, Phillips, is 

 nearly pure carbonate of lime, deposited at 

 the bottom of and around lakes, the waters 

 of Avhibh are impregnated with lime; also 

 in fissures of calcareous rocks, and in lime- 

 stone caverns. It is loose and friable, of 

 white or greyish- white colour, dull and 

 meagre to the touch, soils the fingers, and is 

 so light as to float for a time on water. 



so remote, agate articles are sold in Germany at 

 prices astonishingly low. One other fact, in con- 

 nection with the agate frauds may be worth re- 

 cording. Upper Egypt is known to yield agates, 

 though different from those of South America, 

 and much less abundant. Travellers from Eu- 

 rope in passing through that country enquire for 

 these ; and, to meet the demand, Brazilian agates 

 are now sent to Egypt, and there sold for Egyp- 

 tian agates. At Cairo, especially, numbers are 

 thus disposed of to English and other travellers, 

 who purchase them as souvenirs of the country." 

 — Handbook to the Geology of Wtyrnouth and \ 

 Portland, by R. Damon ; Stanford, i860. 



