Feldspar From Transformer Oil

This large feldspar grain is from an oil sample collected from a 8400kVA transformer. This transformer was reportedly gas blanketed and sealed. The presence of this feldspar particle clearly indicates contamination from the exterior environment. The banding in this particle is typical of many types of feldspars. This banding is most evident near the extinction position when linear crossed polarized light is being used. With circular crossed polarized light the particle would appear uniformly white against the black background but by rotating the analyzer the distinctive banding can be easily seen.