Classification scheme for surface textures of gold nuggets from Finnish Lapland

Abstract

A study was made of the surface textures of about 100 gold nuggets (diameter 2-56 mm) sluiced and panned in the Lemmenjoki, Ivalojoki and Tankavaara areas of northern Finland. The placer gold localities all represent a recently glaciated environment. Surface textures were identified from acetate peels using optical microscopy, image analysis and experimental wear tests. Classification of the surface markings into primary (origin in bedrock), secondary (origin in sediments) and anthropogenic (man-made) groups resulted in a scheme including 6 subgroups and 16 types. The diagnostic features of each surface marking type are described and defined. The relative extents of surface marking types were measured as areal percentages with a point counting procedure, facilitating the comparison of individual nuggets. Applications of the technique range from fingerprinting of individual valuable nuggets in jewellery trade to mineralogical reconnaissance studies as a guide for gold transport.

Keywords

• gold ores
• placers
• nuggets
• surface textures
• classification
• genesis
• Lapland
• Finland