is well-known and may be attributed to the presence of chromium oxide in solid solution,as first suggested by P.Ebell. if one adds larger amounts of chromium salts to the batch a chrome aventurine analogous to the better known copper aventurine may be obtained a demonstrated by Pelouze. Pelouze noted that adding 2.5% potassium dichromate to the batch gave a clear green glass but a few spangles appeared with 5% and 10% gave a good unifrom green aventurine. When examined at 80x under the microscope the crystals appear as grass-green hexagonal platelets in a brighr green matrix. Ebell used the following batch (from which I have calculated the percentage composition of the glass)
He added a sufficient but unspecified amount of pure Cr2O3 to the clear melt so that it gave a uniform green aventurine when the crucible was cooled very slowly in the furmace. The product was broken into small fragments which were treated with hydrofluoric acid vapour then boiled with sulphuric and hydrochloric acids. This released the crystals which had completely sharp corners and edges they thus had not been attacked. After decomposing with sodium carbonate and saltpeter, dissolving in hydrochloric acid, reducing with SO2 and precipitating with ammonia the result was