touchstone

1.
Basalt takes its name from Gk. basanos, "touchstone," a stone used to test gold.

2.
Four words for basalt columns:

cockle
shirl
trap
whin

3.
Webster's 1828 dictionary speaks beautifully of basalt:

A dark, grayish black mineral or stone, sometimes bluish or brownish black, and when withered,the surface is grayish or reddish brown. It is amorphous, columnar, tabular or globular. The columnar form is straight or curved, perpendicular or inclined, sometimes nearly horizontal; the diameter of the columns from three inches to three feet, sometimes with transverse semi-spherical joints, in which the convex part of one is inserted in the concavity of another. The forms of the columns generally are pentagonal, hexagonal, or octagonal. It is sometimes found also in rounded masses, either spherical, or compressed and lenticular. These rounded masses are sometimes composed of concentric layers, with a nucleus, and sometimes of prisms radiating from a center. It is heavy and hard. The pillars of the Giant's causey in Ireland, composed of this stone and exposed to the roughest sea for ages, have their angles as perfect as those at a distance from the waves.