spineln.

1528 MS. List of Jewelry (P.R.O.) xiij rynges,..iij with Spynels,..oon with a crapawd.

1588 T. Hickock tr. C. Federici Voy. & Trauaile f. 29^v Rubyes, Safyres & Spineles.

1620 in R. Sanderson Rymer's Fœdera (1717) XVII. 196 Two greate Stones called Spinnells.

1665 T. Herbert Some Years Trav. (new ed.) 88 Translucent stones which want neither beauty nor esteem; namely, Topazes, Amethysts, Spinels [etc.].

1698 J. Fryer New Acct. E.-India & Persia 214 The third sort of Ruby is called a Spinell.

1801 T. Thomson in Encycl. Brit. Suppl. II. 203/2 If deep [red], the ruby is usually called balass; if pale rosy, spinell.

1892 Daily News 23 Mar. 5/4 The Spinel and the Balas, the one a lively poppy-red, the other a violet-rose, frequently usurp the dignity of a true ruby.

1668 W. Charleton Onomasticon Zoicon 277 Rubinus Spinellus, the Spinel Ruby.

1753 Chambers's Cycl. Suppl. at Ruby The second is the spinal ruby. Under this name they [jewellers] know those rubies, which are of a somewhat less deep..colour, than what they call the true ruby.

1794 R. Kirwan Elements Mineral. (ed. 2) I. 253 Spinell and Balass Rubies.

1815 J. Smith Panorama Sci. & Art II. 411 In the emerald it [sc. chromium] exists in the state of green oxide, and the spinal ruby contains it in the state of an acid.

1839 A. Ure Dict. Arts 391 If..we make the edges of a spinel ruby..curvilinear.

1883 Encycl. Brit. XVI. 386/2 Varieties are—Spinel ruby when scarlet, Balas Ruby when rose-red.

1807 T. Thomson Syst. Chem. (ed. 3) II. 482 This mineral, which has some resemblance to the spinel, was found composed of 60 parts alumina [etc.].

1816 R. Jameson Treat. External Characters Minerals (ed. 2) 127 Triple crystals..occur in spinel and calcareous-spar.

1842 Penny Cycl. XXII. 348/2 Spinell is found in Ceylon and Siam in isolated and rolled crystals in the beds of rivers.

1888 F. Rutley Rock-forming Minerals 108 Ordinary spinel appears reddish, or colourless by transmitted light.

1953 F. H. Pough Field Guide Rocks & Minerals ii. 141 Spinel, like corundum, is a mineral of metamorphosed limestones and low-silica pegmatites, and consequently it is commonly associated with corundum.

1977 A. Hallam Planet Earth 137 The name spinel broadly refers to a group which includes the minerals magnetite and chromite. In a narrower sense, spinel is the magnesium aluminum oxide member of the group.

1837 J. D. Dana Syst. Mineral. 328 The fine colored spinels, when of large size, are highly esteemed as gems.

1863 J. D. Dana Man. Geol. 139 The soft spinels of St. Lawrence co., called houghite.

1880 E. Cleminshaw tr. C. A. Wurtz Atomic Theory 144 The spinels form a very natural isomorphous group.

1944 C. Palache et al. Dana's Syst. Mineral. (ed. 7) I. 688 In addition to the natural spinels a considerable number of artificial spinels have been described, where A = Co, Cd, Cu and B = Co, Ti, Sn, V, Ga, In, Mn. One of the further complexities of composition in the artificial spinels is a tendency for substitution of A atoms for part of the B atoms of the formula, i.e., the formula may be written BABX₄ (as in the compounds GaMgGaO₄, etc.).

1967 D. H. Martin Magnetism in Solids i. 39 The two crystal types to which the most fully investigated ferrimagnetics belong are those known as ‘spinels’ and ‘garnets’.

1974 D. M. Adams Inorg. Solids iii. 69 The structure of a spinel is conveniently described by a parameter γ which equals the fraction of A²⁺ in octahedral sites. Thus, for a ‘normal’ spinel, γ = 0, for an ‘inverse’ spinel, γ = 1. A random distribution of A²⁺ amongst the two groups of sites gives γ = 2/3.

1851 Amer. Jrnl. Sci. 62 210 Some of his specimens are spinel crystals..in one part, and true Houghite in another.

1944 C. Palache et al. Dana's Syst. Mineral. (ed. 7) I. 688 Another chemical feature of interest is the ability of artificial Mg, Al spinel to contain considerable excess of Al₂O₃ without impairment of the spinel structure.

1967 M. Chandler Ceramics in Mod. World vi. 178 Today most ferrites have spinel structures.