Calcite – A common mineral at many locales, Miller Canyon Calcite comes in a variety of hues of orange, red, and pink.
Willemite – Miller Canyon seems to be practically the only locale in Arizona that does not have the yellow/cream variety of Willemite but only has the bright green type that is also found at Franklin. Like New Jersey Willemite it can be strongly phosphorescent. Occasionally Willemite is found that is a blue color in daylight.
Hydrozincite – This mineral is very prevalent at Miller Canyon where it appears to be a weathering of Smithsonite. It can occur as a surface coating, as a concretion in cracks, or infused in Calcite. The color can vary between sky blue, white, gray, and occasionally a periwinkle shade of violet.
Smithsonite – Although rare it is probably the most commonly found mineral after Calcite, Willemite, and Hydrozincite. In other places Smithsonite is commonly found in botryoidal structures but at Miller Canyon I have only seen it occur as a mass or in the textured “dry bone” structure. Often it is found with Willemite or the red/pink variety of Calcite. In some pieces the Calcite and Smithsonite are fused together resulting in a hot pink or lavender color. By itself it is usually a dark violet color.
Powellite – This mineral is rather difficult to find except as small spots. Typically it is found on Calcite and is harder to find with Willemite or Hydrozincite. The color is cream to light yellow. Miller Canyon Powellite fluoresces well under longwave UV, in addition to the usual response under shortwave and midwave.
Scheelite - This mineral is so rare at Miller Canyon that I have found only two specimens, one of which was lost at the collecting area. Scheelite can be differentiated from Powellite by a more white color and lack of a strong longwave response.
Sphalerite – This is usually only found by itself or with Willemite. Occasionally a piece with Calcite is found but other minerals are less likely. Although I have seen Sphalerite occasionally with Hydrozincite I have found fewer with Smithsonite and none with Powellite. Most Miller Canyon Sphalerite is strongly phosphorescent. In fact it has been suggested that the fluorescence seen is in fact all phosphorescence, or delayed fluorescence. One way to observe this is put a piece under UV and note that there is not an immediate response. Over the course of a couple of seconds you can see the Sphalerite “charging up” as it gradually gets brighter. The color of Miller Canyon Sphalerite is yellow/orange. If the fluorescence is less strong then it may appear to be a burnt orange color. The fluorescence is most strong under longwave UV and often there will be little response under shortwave.
Caliche/Aragonite – Although common in other places this is not seen so often at Miller Canyon. The color is either pastel orange or white/blue with phosphorescence. Often the color is hard to distinguish from Hydrozincite but it can be differentiated by the phosphorescence and because it has a strong longwave UV response.
2-color Calcite and Willemite – These are variable, the brightest of which rival pieces from New Jersey. Others are less bright but can come in a fantastic array of patterns.
2-color Calcite and Hydrozincite – Not as common as above.
2-color Willemite and Hydrozincite – This combination is even harder to find and has a special appeal because it represents the “cool” colors. Perhaps it seems a little more organic because it reminds one of trees and sky.
3-color Calcite, Willemite, and Hydrozincite – To me this is the classic Miller Canyon specimen. They come in a variety of brightnesses and patterns
4 or 5-color specimens usually consist of Calcite, Willemite, Hydrozincite, and one or more of the other minerals. They are very rare as the other minerals are typically found on a 2-color or 3-color piece.
“Translucent” assemblage – The Calcite of some pieces is translucent and may encase Willemite or Hydrozincite. Willemite will occur as spots or veins which results in a halo effect around the Willemite. Hydrozincite will occur as a haze, sometimes resulting in a soft pink or violet color from the mix of the Calcite and Hydrozincite fluorescences. These pieces are rare and some of the most sought-after from this locale.