Chondrodite is the most common and most well known member of the Humite
Group of minerals. Members of the Humite Group are noted for having
a mixture of silicate layers and oxide layers in their structures. The
silicate layers have the same structure as olivine.
The oxide layers have the same structure as brucite.
In the case of chondrodite, there are two consecutive olivine layers that
alternate between each brucite layer. The mineral humite,
the next most common member of the group and the group's namesake, has
three olivine layers between each brucite layer.
Chondrodite is not a particularly common mineral and is never seen in
abundance. It is found in hydrothermal deposits and contact and regionally metamorphosed
dolomitic limestones, most notably skarn deposits
and in some serpentinite rocks. Crystals when found are very complex with
many competing forms adding many different and seemingly unrelated faces.
Most often the individual crystals appear rounded or granular. This characteristic
of individual grains lead to its name which is derived from a Greek word
that means, "grain".
- Color is commonly yellow, but also brown, reddish brown and
- Luster is bright vitreous to resinous.
- Transparency: Crystals are translucent with some unusual specimens
- Crystal System: Monoclinic; 2/m
- Crystal Habits include stubby prismatic to tabular or rounded
crystals, but as is most commonly the case, as embedded grains. Good crystals
show multiple facets without discernible symmetry. Also found massive.
- Cleavage is good in one direction, basal, (not always discernible
- Fracture is subconchoidal.
- Hardness is 6 - 6.5
- Specific Gravity is 3.1 - 3.2
- Streak is white.
- Other Characteristics: Twinning
may be seen as lamellar striations and some specimens display yellow fluorescence.
- Associated Minerals include
magnetite, diopside, spinel
, wollastonite, monticellite
serpentine, clinochlore, olivine and
- Notable Occurrences are include Monte Somma, Mount Vesuvius,
Italy; Paragas, Finland; Kafveltorp, Sweden; and Franklin, New Jersey;
Tilly Foster Mine, Brewster, New York; Riverside County, California and
- Best Field Indicators are crystal habit, color, luster, cleavage, environment of formation