Datolite - Cloverdale, Mendocino County, California???

Contributed by: Mark Cole
Date: Mar 23rd, 2026
Locality: Rosenhahnite occurrence, Russian River, Cloverdale area, Mendocino County, California, USA (See on Mindat)
Size: 3 x 4.5 cm

Description:
There is some concern about the exact locality of this mineral (although the ID label was very specific). It is reported that FMS members in the Northern California region bought all the Datolite the Crafty Lady Rock Shop had and resold what they did not want to keep. Per one of our contributors: "Here is what I am guessing happened. The Crafty Lady did not have a location for this material, so people labeled this as: From Crafty Lady Rock Shop, Hopland, Mendocino Co., California. As the specimens were sold, the location was shortened to Hopland, Mendocino Co., California. Someone wanted to get a more accurate location, so they looked for a nearby Datolite location in Mindat and found the Rosenhahnite occurrence. The Datolite from the Rosenhahnite occurrence looks nothing like the Crafty Lady specimens."

Originally posted by Mark Cole on Nature's Rainbows in 2015.

UPDATE: This specimen is now in the collection of Michael Crawford. He provided the normal light and LW images. The datolite fluorescence is the same for all wavelengths of UV light. Another Northern California datolite specimen in the owner's collection with similar fluorescent properties comes from Healdsburg, Sonoma County, California.

Fluorescence under shortwave UV light. Mark Cole photograph from original post.

Fluorescence under longwave UV light.

Normal light.

Summary of luminescence responses:

Datolite (Mindat) (RRUFF)

• Fluorescence under Longwave (365nm LED) UV light: Yellow
• Fluorescence under Midwave (305nm LED) UV light: Yellow
• Fluorescence under Shortwave (255nm LED) UV light: Yellow