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Formula: Ca(C2H3O3)2.3H2O
Hydrated organic compound, glycolate subgroup
Crystal system: Triclinic
Specific gravity: 1.53 measured, 1.55 calculated for the empirical formula
Hardness: 1
Colour: Colourless to white
Solubility: At room temperature, insoluble in water but slowly dissolves in dilute hydrochloric acid
Environments
Hydrothermal environments, organic mineral
Since the discovery of the first glycolate mineral, lazaraskeite, from
the western end of Pusch Ridge in the Santa Catalina Mountains, Tucson, Arizona, USA, at least eight other glycolate
minerals have been identified from the same locality, namely
domitrovicite, fuchunite,
glecklerite, jimkrieghite,
lianbinite, puschridgeite,
rasmussenite and stanevansite.
Rasmussenite is a new mineral, approved in 2024 and to date (October 2025) reported only from the type
locality.
Localities
At the type locality, Western end, Pusch Ridge, Pima County, Arizona, USA, rasmussenite occurs in a heavily
fractured leucogranite, 1 to 2 m below the rock surface.
Associated minerals include chrysocolla,
hematite, lazaraskeite,
microcline, phlogopite,
quartz and stanevansite.
Rasmussenite is a secondary mineral believed to have
formed through the interaction of fluids containing glycolic acid, C2H4O3 derived
from decaying plant materials, plant root exudates, or bacterial activities with Ca produced by the alteration of
primary and secondary minerals in the host rock.
Rasmussenite occurs as sprays or spherical aggregates of fibrous or acicular crystals, with individual
crystals up to 0.30 x 0.01 x 0.01 mm3. It is colourless and transparent with a white streak and vitreous
lustre
(CJMP 63.4.385–395).
Rasmussenite from the Pusch Ridge -
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