51�Թ�

Common topaz is found in masses by the hundredweight in the neighbourhood of Falun; common emerald is found in thick crystals several feet in length in felspar quarries, in Roslagen, and in Tammela and Kisko parishes in Finland; common spinel occurs abundantly in Åker limestone quarry; common zircon at Brevig in Norway, and turquoise-like but badly coloured stones at Vestanå in Skane.

The most skilful chemist would thus have difficulty in finding in their chemical composition the least difference between corundum and sapphire or ruby, between common beryl and emerald, between the precious and the common topaz, between the hyacinth and the common zircon, between precious and common spinel; and every mineralogist knows that there are innumerable intermediate stages between these minerals which are so dissimilar though absolutely identical in composition.