Multi-wavelength Tenebrescent Hackmanite - Davis Quarry, Hastings County, Ontario, Canada

Contributed by: FMS Admin
minID: 0DT-NPA
Date: May 17th, 2026
Locality: Davis Quarry, Dungannon Township, Town of Bancroft, Hastings County, Ontario, Canada (See on Mindat)
Size: 5.4 x 4.9 x 8.8 cm

Description:
Beautiful specimen of sodalite var. hackmanite, from the now inaccessible Davis Quarry, near Bancroft. This specimen was given to me by a collector in Quadeville, Ontario; according to him, this quality is pretty much the best that was found in this quarry, and nearly impossible to find on the market nowadays. Based on other specimens I've seen, I have no problem believing this; other specimens I have seen were much less tenebrescent and did not fluoresce as bright as this one.

Under shortwave UV, the fluorescence shifts to a redder color once the tenebrescence sets in. Two pictures below show the initial shortwave fluorescence and the red shift after about 15 seconds of shortwave UV exposure.

Originally posted by Frédéric Messier Leroux on Nature's Rainbows in 2021.

Fluorescence under longwave UV light.

Fluorescence under midwave UV light.

Fluorescence under shortwave UV light. Initial fluorescence.

Fluorescence under shortwave UV light. After 15 seconds of UV exposure.

Tenebrescence after exposure to longwave UV light.

Tenebrescence after exposure to shortwave UV light.

Afterglow after exposure to shortwave UV light.

Normal light.

Summary of luminescence responses:

Hackmanite (Mindat) (RRUFF)

• Fluorescence under Longwave (365nm LED) UV light: Orange
• Fluorescence under Midwave (305nm LED) UV light: Orange
• Fluorescence under Shortwave (255nm LED) UV light: Red
• Tenebrescence after exposure to Longwave (365nm LED) UV light: Purple
• Tenebrescence after exposure to Shortwave (255nm LED) UV light: Purple
• Afterglow after exposure to Shortwave (255nm LED) UV light: White