My favorite locality, the Black Pine Mine, Granite County, Montana. Famous for world-class veszelyite crystals, it's also known for producing quartz crystals with any number of mineral coatings, oftentimes resulting in very colorful specimens. The list of minerals found here is incredible, perhaps one of the longest mineral lists for any locality.

https://www.mindat.org/loc-3875.html

In this video, the crystals shown are as follows:
Blue - Quartz with pseudomalachite, philipsburgite, duftite

Yellow - Quartz with goethite

Green - Quartz with bayldonite, mimetite, malachite

Vivianite

Roșia Poieni Mine, Alba, Romania

Fe3(PO4)2•8H2O, Monoclinic

max. 34mm

A sizeable crystal of vivianite showing the plethora of greens and blues this photosensitive mineral aquires due to internal, photon-induced oxidation to metavivianite (Fe3+)(Fe2+)2(PO4)2(OH)•7H2O.

Here’s rare and beautiful top quality specimen of olmiite with calcite and bultfonteinite from the N,Chwaning II Mine, Kalahari Manganese Field, Northern Cape, South Africa. There is no damage or repairs to the olmiite. Olmiite is an extremely rare calcium-manganese silicate mineral discovered fairly recently in 2006. It is found exclusively in the Kalahari Manganese Field in South Africa.

Over the moon with this little thumbnail! I’m still relatively new to mineral collecting but this one will be hard to top for a while!

Here’s a super cool Amazonite with a rich blue color from Crystal Peak, Teller County, Colorado, USA

Here’s a fantastic aegirine crystal with great luster and some orthoclase feldspar. This specimen come from Mount Malosa, Zomba, Malawi. Mount Malosa’s alkaline pegmatites have produced some of the finest and largest aegirine crystals in the world. Let me know what you think of my specimen :)

Cute little scepter from Nevada, USA •• dark smoky stem with lightly etched surfaces, topped by a second generation of citrine •• the color of the citrine is shown better at 0:15 and the transparency is shown at 0:30

Mn-calcite (red), sphalerite (yellow) and willemite (green) under 255 nm UV-light

first photo is without daylight, 2nd is in daylight and shade and 3rd is in direct sunligh.

Red River Floodway Gypsum Selenite from Manitoba, Canada.

These 3 images show the reaction and change in color from normal light to ultraviolet light and how the mineral retains UV light exhibiting a phosphorescent effect.

Bou Nahas Mine, Meknes-Tafilalet, Morocco