Hogarthite
Chemical formula: (Na,K)<sub>2</sub>CaTi<sup>4+</sup><sub>2</sub>Si<sub>10</sub>O<sub>26</sub>·8H<sub>2</sub>O
Hogarthite is a very rare mineral from the silicate group, forming colorless to white, acicular crystals in phonolite vugs.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 2.45
- Cleavage
- Good on {100} and {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identification of hogarthite is based on its characteristic form – fine, acicular, colorless crystals forming radial aggregates. Its specific occurrence environment in miarolitic vugs within phonolite is also crucial. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). ## Distinguishing from similar minerals It can be confused with other acicular zeolites or silicates found in similar environments, such as natrolite or aegirine. Visual differentiation is practically impossible and requires specialized studies. Hogarthite is distinguished by its unique chemical composition, containing titanium. ## Crystal forms It forms elongated, acicular or bladed crystals, often flattened. These crystals combine into radial, stellate, or chaotically tangled aggregates filling small voids in the host rock.
Geological environment
## Genesis Hogarthite is a hydrothermal mineral. It crystallizes in a late stage from residual solutions in miarolitic vugs and gas vesicles within phonolitic volcanic rocks. ## Mineral associations At its type locality (Mont Saint-Hilaire), it co-occurs with many other rare minerals, such as analcime, microcline, aegirine, natrolite, sérandite, eudialyte, steacyite, leifite, and catapleiite. ## Localities It is an extremely rare mineral, currently known only from its type locality: the Poudrette quarry at Mont Saint-Hilaire, in the Montérégie region of Quebec, Canada.
Rarity
Extremely rare
For collectors
## Quality criteria For collectors, the size and quality of the crystal aggregates formed are most important. The most desirable specimens are those with well-formed, radial rosettes of acicular crystals, contrasting with the darker host rock. Association with other rare minerals from Mont Saint-Hilaire is also significant. ## Popular localities The only source of hogarthite specimens is the Poudrette quarry at Mont Saint-Hilaire in Canada, which is world-renowned for hundreds of unique and rare minerals.
Care and storage
## Cleaning Due to the extreme delicacy and small size of the crystals, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust. Avoid contact with water and other chemicals. ## What to avoid Avoid ultrasonics, steam cleaners, acids, and all solvents. The crystals are brittle and sensitive to mechanical shocks. As a hydrated mineral, it may be sensitive to changes in temperature and humidity, which can lead to its dehydration and destruction. ## Storage Specimens should be stored under stable conditions, in sealed "micromount" containers, to protect them from dust, mechanical damage, and sudden changes in humidity. Avoid exposure to direct sunlight and heat sources.