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A series of highly altered diabase rocks showing macroscopically in part the typical ophitique structure. Under the microscope only one of these very interesting rocks is studied Pyroxene is completely replaced by a green, fibrous, uralitic hornblende. The plagioclase, which has macroscopically a sausseritic appearance, has suffered an entire change to a mineral of the scapolite group, zoisite and tremolite. The first mineral makes large colorless irregular patches, resembling in sections parallel to the c axis muscovite by virtue of its distinct cleavage cracks, its high double refraction and the extinction parallel to the cleavage cracks. But they are to be distinguished, for in scapolite the optic elasticity parallel to the cleaveage cracks is greater than perpendicular to that direction; in muscovite the opposite is true. Sections perpendicular to the c axis show two sets of cleavage cracks perpendicular to each other, and give in convergent light a very distinct uniaxial figure of negative character, a dark cross, and one ring. Through these scapolite patches are scattered colorless or cloudy grains of high refraction and low double refraction, presenting between crossed nicols a bluish gray polarization color like melilite. These grains belong to zoisite. In addition a colorless hornblende (tremolite) in needles perforates the zoisite and scapolite. A somewhat bleached biotite in irregular patches may be a primary component. It contains small colorless needles arranged in three directions (cutting each other under 60 degrees) probably parallel to the pressure figure (this could not be decided on account of the lack of crystallographic shape of the mica). The arrangement is the same, as it occurs often with inclusions of rutile in mica, but the inclosed needles show much smaller refraction and double refraction than rutile and an extinction oblique to their length. As far as can be determined without a chemical examination, the needles belong to the above mentioned colorless hornblende (tremolite). Grains of ilmenite are surrounded by a big corona of cloudy leucoxene. Close by the leucoxene, and sometimes included in biotite, there are seen minute crystals showing an acute pyramid, very high refraction, double refraction and all the properties of anatase.

The whole mineralogical composition of the aforesaid diabase indicates an alteration made by dynamo-metamorphism.

There are some fine-grained rock specimens showing a pale green or gray color and jointed in plates. Under the microscope it is seen that they consist of long needles of tremolite and grains of epidote, both in variable amount, but making up generally three-quarters of the whole rock; calcite is also found in irregular spots, and a colorless mineral which belongs to quartz. So far as can be said, without a geological investigation in the field, these rocks belong to diabases representing the highest stage in the mentioned alteration.