Spencer Opal Mine, Spencer, Clark County, Idaho, USAi

Regional Level Types
Spencer Opal Mine	Mine
Spencer	- not defined -
Clark County	County
Idaho	State
USA	Country

Colour: Body colour is most often white, but less frequently yellow to ochre and, more rarely, pink or even purple. These colours are thought to be due to manganese and iron.

Fluorescence: The green luminescence (mainly seen under SWUV) is characterised by a range of bands at around 504, 525, and 547 nm accompanied by two shoulders at around 572 and 602 nm (Figure 19). This result corresponds to the classical emission of uranyl ions (UO2)2+, which are often seen in opal [35,41]. The orange-red fluorescence under LWUV and SWUV presents an emission spectrum consisting of a broad band centred around 630 nm, i.e., in the orange (Figure 20), accompanied by numerous, there are relatively sharp peaks between 680 and 820 nm (i.e., in the red and NIR part). Orange luminescence is rare in opals, and it is generally believed to be generated by quinones in pink opals. Quinones are characterised by two major bands around 580 and 620 nm. This is very different from the present spectrum. In addition, in Idaho, the orange luminescence does not correspond to the pink colour, as is the case for quinone-coloured opals.

Description: Extremely rare star opals have also occasionally been found in this mine