Mercury

Mercury is the prince in planetary kingdom. If it is conjoined with malefic then it acts as a malefic and vice versa. It controls wit and logic. Thus it should be benefic in chart. If it is not a benefic planet then one can recite the following mantras to appease mercury:

Vedic mantra:

ऊँ उद्बुध्यस्वाग्ने प्रतिजागृहि त्वमिष्टापूर्ते स सृजेथामयं च।

अस्मिन्त्सधस्थे अध्युत्तरस्मिन्विश्वे देवा यजमानश्च सीदत।।

Gayatri Mantra

ऊँ चन्द्रपुत्राय विदमहे रोहिणी प्रियाय धीमहि तन्नोबुध: प्रचोदयात।

Beej mantra

ऊं बुं बुधाय नम:।

Tantrik mantra

ऊँ ऎं स्त्रीं श्रीं बुधाय नम:

ऊँ ब्रां ब्रीं ब्रौं स: बुधाय नम:

ऊँ स्त्रीं स्त्रीं बुधाय नम:

Emerald is the stone for Mercury. If one cannot buy this then one can purchase green zircon, green agate, green firoza as substones.